diff --git a/README.md b/README.md
index bebab0c..8598879 100644
--- a/README.md
+++ b/README.md
@@ -3,52 +3,70 @@
 [GS Open Source](https://garrity.co/oss.html) |
 [License (Apache 2.0)](./LICENSE)
 
-Garrity Software standard types and operations. Provides a zero-dependency
-collection of basic tools.
+Garrity Software standard types and operations with minimal dependencies.
 
 - [Usage](#usage)
-    - [Dependency](#dependency)
-- [Donate](#donate)
+- [Core Module](#core-module)
+- [I/O Module](#io-module)
+- [Effect Module](#effect-module)
 
 ## Usage
 
-### Dependency
-
 This artifact is available in the Garrity Software Maven repository.
 
 ```scala
 externalResolvers +=
   "Garrity Software Releases" at "https://maven.garrity.co/releases"
 
-val GsStd: ModuleID =
-  "gs" %% "gs-std-v0" % "$VERSION"
+// No Dependencies
+val GsStdCore: ModuleID =
+  "gs" %% "gs-std-core-v0" % "$VERSION"
+
+// Depends on Cats Effect and Fs2
+val GsStdIO: ModuleID =
+  "gs" %% "gs-std-io-v0" % "$VERSION"
+
+// Depends on Cats Effect and Fs2
+val GsStdEffect: ModuleID =
+  "gs" %% "gs-std-effect-v0" % "$VERSION"
 ```
 
-## Types
+## Core Module
 
-- `Nat`
-- `Size`
-- `ByteCount`
-- `Blob`
-- `CreatedAt`
-- `UpdatedAt`
-- `SHA256`
-- `MD5`
-- `EncodedString`
-- `B64`
-- `B64Url`
-- `Hex`
+Provides standard types, wrappers, and tools.
 
-## Tools
+- Common semantic types (e.g. `CreatedAt`).
+- Encoding and representing encoded data.
+- Hashing algorithms and representing hashes.
+- Reasoning about bytes and blobs.
 
-- `Encoder`
-- `Base64Encoder`
-- `HexEncoder`
-- `Decoder`
-- `Base64Decoder`
-- `HexDecoder`
+## I/O Module
 
-## Donate
+### File Helpers
 
-Enjoy this project or want to help me achieve my [goals](https://garrity.co)?
-Consider [Donating to Pat on Ko-fi](https://ko-fi.com/gspfm).
+`Files`: These provide support for reading and writing files. Provides wrapping
+around `java.nio.file.Files`.
+
+Note that for streaming operations, `fs2.io` provides everything conveniently
+and does not benefit from wrapping.
+
+### Resource Helpers
+
+These provide support for reading files from packaged resource directories
+(e.g. `src/main/resources`).
+
+## Effect Module
+
+This module relies on the [Core Module](#core-module) and takes advantage of the
+types defined therein.
+
+### Random Numbers
+
+`Rng[F[_]]`: Effectful random number generator with creation/testing
+helpers.
+
+### Dates and Times
+
+`DateTimeProvider[F[_]]`: Effectful provider for dates and times. Provides an
+implementation based on clock injection. Helps to decouple date/time use from
+static methods.
diff --git a/build.sbt b/build.sbt
index f2d5856..fed8107 100644
--- a/build.sbt
+++ b/build.sbt
@@ -10,6 +10,10 @@ ThisBuild / licenses := Seq(
   )
 )
 
+val noPublishSettings = Seq(
+  publish := {}
+)
+
 val sharedSettings = Seq(
   scalaVersion               := scala3,
   version                    := semVerSelected.value,
@@ -18,14 +22,61 @@ val sharedSettings = Seq(
   coverageMinimumBranchTotal := 100
 )
 
+val Deps = new {
+
+  val Cats = new {
+    val Core: ModuleID   = "org.typelevel" %% "cats-core"   % "2.13.0"
+    val Effect: ModuleID = "org.typelevel" %% "cats-effect" % "3.7.0"
+  }
+
+  val Fs2 = new {
+    val Core: ModuleID = "co.fs2" %% "fs2-core" % "3.13.0"
+    val IO: ModuleID   = "co.fs2" %% "fs2-io"   % "3.13.0"
+  }
+
+  val MUnit: ModuleID = "org.scalameta" %% "munit" % "1.3.0" % Test
+}
+
 lazy val testSettings = Seq(
   libraryDependencies ++= Seq(
-    "org.scalameta" %% "munit" % "1.3.0" % Test
+    Deps.MUnit
   )
 )
 
 lazy val `gs-std` = project
   .in(file("."))
+  .aggregate(core, io, effect)
   .settings(sharedSettings)
   .settings(testSettings)
   .settings(name := s"${gsProjectName.value}-v${semVerMajor.value}")
+
+lazy val core = project
+  .in(file("modules/core"))
+  .settings(sharedSettings)
+  .settings(testSettings)
+  .settings(name := s"${gsProjectName.value}-core-v${semVerMajor.value}")
+
+lazy val io = project
+  .in(file("modules/io"))
+  .settings(sharedSettings)
+  .settings(testSettings)
+  .settings(name := s"${gsProjectName.value}-io-v${semVerMajor.value}")
+  .settings(
+    libraryDependencies ++= Seq(
+      Deps.Cats.Core,
+      Deps.Cats.Effect,
+      Deps.Fs2.Core,
+      Deps.Fs2.IO
+    )
+  )
+
+lazy val effect = project
+  .in(file("modules/effect"))
+  .dependsOn(core)
+  .dependsOn(io % "test->compile")
+  .settings(sharedSettings)
+  .settings(testSettings)
+  .settings(name := s"${gsProjectName.value}-effect-v${semVerMajor.value}")
+  .settings(
+    libraryDependencies ++= Seq(Deps.Cats.Core, Deps.Cats.Effect, Deps.Fs2.Core)
+  )
diff --git a/src/main/scala/gs/std/v0/Base64Decoder.scala b/modules/core/src/main/scala/src/gs/std/v0/core/Base64Decoder.scala
similarity index 97%
rename from src/main/scala/gs/std/v0/Base64Decoder.scala
rename to modules/core/src/main/scala/src/gs/std/v0/core/Base64Decoder.scala
index f789979..7cc8c1c 100644
--- a/src/main/scala/gs/std/v0/Base64Decoder.scala
+++ b/modules/core/src/main/scala/src/gs/std/v0/core/Base64Decoder.scala
@@ -1,4 +1,4 @@
-package gs.std.v0
+package gs.std.v0.core
 
 import java.{util => ju}
 
diff --git a/src/main/scala/gs/std/v0/Base64Encoder.scala b/modules/core/src/main/scala/src/gs/std/v0/core/Base64Encoder.scala
similarity index 97%
rename from src/main/scala/gs/std/v0/Base64Encoder.scala
rename to modules/core/src/main/scala/src/gs/std/v0/core/Base64Encoder.scala
index 935cdfd..9c99fa1 100644
--- a/src/main/scala/gs/std/v0/Base64Encoder.scala
+++ b/modules/core/src/main/scala/src/gs/std/v0/core/Base64Encoder.scala
@@ -1,4 +1,4 @@
-package gs.std.v0
+package gs.std.v0.core
 
 import java.nio.charset.Charset
 import java.nio.charset.StandardCharsets
diff --git a/modules/core/src/main/scala/src/gs/std/v0/core/Blob.scala b/modules/core/src/main/scala/src/gs/std/v0/core/Blob.scala
new file mode 100644
index 0000000..b51d956
--- /dev/null
+++ b/modules/core/src/main/scala/src/gs/std/v0/core/Blob.scala
@@ -0,0 +1,49 @@
+package gs.std.v0.core
+
+import java.util.Base64
+
+/** Represents a blob -- some array of bytes.
+  *
+  * @param data
+  *   The underlying data.
+  */
+final class Blob(private val data: Array[Byte]) extends IndexedSeq[Byte]:
+
+  /** @inheritDocs
+    */
+  override def apply(i: Int): Byte = byteAt(i)
+
+  /** @inheritDocs
+    */
+  override def length: Int = data.length
+
+  /** @return
+    *   The number of bytes in this blob, expressed as a count.
+    */
+  def numberOfBytes: ByteCount = ByteCount(data.length)
+
+  /** @inheritDocs
+    */
+  override def equals(obj: Any): Boolean =
+    obj match
+      case other: Blob        => data.sameElements(other.data)
+      case other: Array[Byte] => data.sameElements(other)
+      case _                  => false
+
+  /** @inheritDocs
+    */
+  override def hashCode(): Int = data.hashCode()
+
+  /** Retrieve the byte at the given index.
+    *
+    * @param index
+    *   The index.
+    * @return
+    *   The byte stored at the given index.
+    */
+  def byteAt(index: Int): Byte = data.apply(index)
+
+  /** @return
+    *   This byte array, encoded as a base64 string.
+    */
+  def base64(): String = Base64.getEncoder().encodeToString(data)
diff --git a/modules/core/src/main/scala/src/gs/std/v0/core/ByteCount.scala b/modules/core/src/main/scala/src/gs/std/v0/core/ByteCount.scala
new file mode 100644
index 0000000..c59033d
--- /dev/null
+++ b/modules/core/src/main/scala/src/gs/std/v0/core/ByteCount.scala
@@ -0,0 +1,138 @@
+package gs.std.v0.core
+
+/** Opaque type for some number of bytes (>= 0).
+  */
+opaque type ByteCount = Long
+
+/** Opaque type for some number of bytes (>= 0).
+  */
+object ByteCount:
+
+  /** 0 bytes.
+    */
+  final val Zero: ByteCount = 0
+
+  /** 1,000 bytes.
+    */
+  final val OneKilobyte: ByteCount = 1000
+
+  /** 1,000,000 bytes.
+    */
+  final val OneMegabyte: ByteCount = 1000000
+
+  /** 1,000,000,000 bytes.
+    */
+  final val OneGigabyte: ByteCount = 1000000000
+
+  /** Express the given number as a byte count. All values are normalized to the
+    * absolute value -- negative values are coerced to positive.
+    *
+    * @param value
+    *   The input integer.
+    * @return
+    *   The [[ByteCount]] instance.
+    */
+  def apply(value: Long): ByteCount = Math.abs(value)
+
+  /** 1 kilobyte = 1,000 bytes
+    *
+    * @param kb
+    *   The number of kilobytes.
+    * @return
+    *   The number of bytes.
+    */
+  def fromKilobytes(kb: Long): ByteCount =
+    Math.abs(kb) * 1000L
+
+  /** 1 megabyte = 1,000,000 bytes
+    *
+    * @param mb
+    *   The number of megabytes.
+    * @return
+    *   The number of bytes.
+    */
+  def fromMegabytes(mb: Long): ByteCount =
+    Math.abs(mb) * 1000000L
+
+  /** 1 gigabyte = 1,000,000,000 bytes
+    *
+    * @param mb
+    *   The number of gigabytes.
+    * @return
+    *   The number of bytes.
+    */
+  def fromGigabytes(gb: Long): ByteCount =
+    Math.abs(gb) * 1000000000
+
+  given CanEqual[ByteCount, ByteCount] = CanEqual.derived
+
+  given Ordering[ByteCount] with
+
+    /** @inheritDocs
+      */
+    def compare(
+      x: ByteCount,
+      y: ByteCount
+    ): Int =
+      if x > y then 1 else if x == y then 0 else -1
+
+  extension (byteCount: ByteCount)
+    /** @return
+      *   The underlying `Long`.
+      */
+    def unwrap(): Long = byteCount
+
+    /** @return
+      *   The underlying `Long`.
+      */
+    def toLong(): Long = byteCount
+
+    /** 1 kilobyte = 1,000 bytes
+      *
+      * @return
+      *   The number of kilobytes represented by this count.
+      */
+    def toKilobytes(): Double = byteCount / 1000.0
+
+    /** 1 megabyte = 1,000,000 bytes.
+      *
+      * @return
+      *   The number of megabytes represented by this count.
+      */
+    def toMegabytes(): Double = byteCount / 1000000.0
+
+    /** 1 gigabyte = 1,000,000,000 bytes.
+      *
+      * @return
+      *   The number of gigabytes represented by this count.
+      */
+    def toGigabytes(): Double = byteCount / 1000000000.0
+
+    /** Add some count to this one.
+      *
+      * @param that
+      *   The number to add.
+      * @return
+      *   The sum of the numbers.
+      */
+    def +(that: ByteCount): ByteCount = byteCount + that
+
+    /** Multiply this count by some other count.
+      *
+      * @param that
+      *   The number to multiply by.
+      * @return
+      *   The product of the numbers.
+      */
+    def *(that: ByteCount): ByteCount = byteCount * that
+
+    /** Check if this value is the same as some number.
+      *
+      * @param value
+      *   The number to compare against.
+      * @return
+      *   True if the values are equal, false otherwise.
+      */
+    def equal(value: Int): Boolean = byteCount == value.toLong
+
+end ByteCount
diff --git a/modules/core/src/main/scala/src/gs/std/v0/core/CreatedAt.scala b/modules/core/src/main/scala/src/gs/std/v0/core/CreatedAt.scala
new file mode 100644
index 0000000..16c0a6b
--- /dev/null
+++ b/modules/core/src/main/scala/src/gs/std/v0/core/CreatedAt.scala
@@ -0,0 +1,37 @@
+package gs.std.v0.core
+
+import java.time.Instant
+
+/** Opaque type that represents the instant something was created.
+  */
+opaque type CreatedAt = Instant
+
+/** Opaque type that represents the instant something was created.
+  */
+object CreatedAt:
+
+  /** Instantiate a new [[CreatedAt]] from the given `java.time.Instant`.
+    *
+    * @param value
+    *   The value to semantically represent.
+    * @return
+    *   The new [[CreatedAt]].
+    */
+  def apply(value: Instant): CreatedAt = value
+
+  given CanEqual[CreatedAt, CreatedAt] = CanEqual.derived
+
+  given Ordering[CreatedAt] = Ordering[Instant]
+
+  extension (createdAt: Instant)
+    /** @return
+      *   The underlying `java.time.Instant`.
+      */
+    def unwrap(): Instant = createdAt
+
+    /** @return
+      *   The underlying `java.time.Instant`.
+      */
+    def toInstant(): Instant = createdAt
+
+end CreatedAt
diff --git a/modules/core/src/main/scala/src/gs/std/v0/core/Decoder.scala b/modules/core/src/main/scala/src/gs/std/v0/core/Decoder.scala
new file mode 100644
index 0000000..3ebd2a4
--- /dev/null
+++ b/modules/core/src/main/scala/src/gs/std/v0/core/Decoder.scala
@@ -0,0 +1,13 @@
+package gs.std.v0.core
+
+/** Interface for byte decoding from encoded String formats.
+  */
+trait Decoder[-A <: EncodedString]:
+  /** Decode an input string to an array of bytes.
+    *
+    * @param input
+    *   The input to decode.
+    * @return
+    *   The decoded byte array.
+    */
+  def decode(input: A): Array[Byte]
diff --git a/src/main/scala/gs/std/v0/Encode.scala b/modules/core/src/main/scala/src/gs/std/v0/core/Encode.scala
similarity index 98%
rename from src/main/scala/gs/std/v0/Encode.scala
rename to modules/core/src/main/scala/src/gs/std/v0/core/Encode.scala
index f1d1222..0059eeb 100644
--- a/src/main/scala/gs/std/v0/Encode.scala
+++ b/modules/core/src/main/scala/src/gs/std/v0/core/Encode.scala
@@ -1,4 +1,4 @@
-package gs.std.v0
+package gs.std.v0.core
 
 import java.nio.charset.Charset
 import java.nio.charset.StandardCharsets
diff --git a/src/main/scala/gs/std/v0/EncodedString.scala b/modules/core/src/main/scala/src/gs/std/v0/core/EncodedString.scala
similarity index 96%
rename from src/main/scala/gs/std/v0/EncodedString.scala
rename to modules/core/src/main/scala/src/gs/std/v0/core/EncodedString.scala
index 840b031..372b7e5 100644
--- a/src/main/scala/gs/std/v0/EncodedString.scala
+++ b/modules/core/src/main/scala/src/gs/std/v0/core/EncodedString.scala
@@ -1,4 +1,4 @@
-package gs.std.v0
+package gs.std.v0.core
 
 /** Represents string-encoded data.
   *
@@ -51,8 +51,8 @@ final class B64(
 
 object B64:
 
-  /** Instantiate [[B64]] from the given string. Assumes that the input is 
-   *  base64-encoded.
+  /** Instantiate [[B64]] from the given string. Assumes that the input is
+    * base64-encoded.
     *
     * This function does NOT validate the input.
     *
@@ -97,8 +97,8 @@ final class B64Url(
 
 object B64Url:
 
-  /** Instantiate [[B64Url]] from the given string. Assumes that the input is 
-   *  base64-encoded.
+  /** Instantiate [[B64Url]] from the given string. Assumes that the input is
+    * base64-encoded.
     *
     * This function does NOT validate the input.
     *
@@ -143,8 +143,8 @@ final class Hex(
 
 object Hex:
 
-  /** Instantiate [[Hex]] from the given string. Assumes that the input is 
-   *  hex-encoded.
+  /** Instantiate [[Hex]] from the given string. Assumes that the input is
+    * hex-encoded.
     *
     * This function does NOT validate the input.
     *
diff --git a/src/main/scala/gs/std/v0/Encoder.scala b/modules/core/src/main/scala/src/gs/std/v0/core/Encoder.scala
similarity index 97%
rename from src/main/scala/gs/std/v0/Encoder.scala
rename to modules/core/src/main/scala/src/gs/std/v0/core/Encoder.scala
index 89dbc6d..1278aeb 100644
--- a/src/main/scala/gs/std/v0/Encoder.scala
+++ b/modules/core/src/main/scala/src/gs/std/v0/core/Encoder.scala
@@ -1,4 +1,4 @@
-package gs.std.v0
+package gs.std.v0.core
 
 import java.nio.charset.Charset
 import java.nio.charset.StandardCharsets
diff --git a/src/main/scala/gs/std/v0/HexDecoder.scala b/modules/core/src/main/scala/src/gs/std/v0/core/HexDecoder.scala
similarity index 95%
rename from src/main/scala/gs/std/v0/HexDecoder.scala
rename to modules/core/src/main/scala/src/gs/std/v0/core/HexDecoder.scala
index d5159a6..c48c1e3 100644
--- a/src/main/scala/gs/std/v0/HexDecoder.scala
+++ b/modules/core/src/main/scala/src/gs/std/v0/core/HexDecoder.scala
@@ -1,4 +1,4 @@
-package gs.std.v0
+package gs.std.v0.core
 
 import java.util.HexFormat
 
diff --git a/src/main/scala/gs/std/v0/HexEncoder.scala b/modules/core/src/main/scala/src/gs/std/v0/core/HexEncoder.scala
similarity index 92%
rename from src/main/scala/gs/std/v0/HexEncoder.scala
rename to modules/core/src/main/scala/src/gs/std/v0/core/HexEncoder.scala
index c6960c1..7430199 100644
--- a/src/main/scala/gs/std/v0/HexEncoder.scala
+++ b/modules/core/src/main/scala/src/gs/std/v0/core/HexEncoder.scala
@@ -1,4 +1,4 @@
-package gs.std.v0
+package gs.std.v0.core
 
 import java.util.HexFormat
 
diff --git a/modules/core/src/main/scala/src/gs/std/v0/core/MD5.scala b/modules/core/src/main/scala/src/gs/std/v0/core/MD5.scala
new file mode 100644
index 0000000..e4866d5
--- /dev/null
+++ b/modules/core/src/main/scala/src/gs/std/v0/core/MD5.scala
@@ -0,0 +1,108 @@
+package gs.std.v0.core
+
+import java.nio.charset.Charset
+import java.nio.charset.StandardCharsets
+import java.security.MessageDigest
+
+/** Opaque type representing a MD5 hash.
+  */
+opaque type MD5 = Array[Byte]
+
+/** Opaque type representing a MD5 hash.
+  */
+object MD5:
+
+  /** MD5 hashes are exactly 16 bytes.
+    */
+  final val NumberOfBytes: ByteCount = ByteCount(16)
+
+  /** The algorithm name is "MD5".
+    */
+  final val Algorithm: String = "MD5"
+
+  /** Instantiate a [[MD5]] from the given byte array. This function does not
+    * know whether the array is actually a calculated hash.
+    *
+    * Typically used for loading pre-validated hashes (e.g. from a database).
+    *
+    * @param bytes
+    *   The bytes - must contain exactly 16 bytes.
+    * @return
+    *   The new [[MD5]] instance.
+    */
+  def fromBytes(bytes: Array[Byte]): MD5 =
+    if NumberOfBytes.equal(bytes.length) then bytes
+    else
+      throw IllegalArgumentException(
+        s"MD5 values must be exactly $NumberOfBytes bytes."
+      )
+
+  /** Calculate the MD5 hash for the given byte array.
+    *
+    * @param data
+    *   The byte array.
+    * @return
+    *   The calculated [[MD5]].
+    */
+  def calculate(data: Array[Byte]): MD5 =
+    MessageDigest.getInstance(Algorithm).digest(data)
+
+  /* Calculate the MD5 hash for the given string.
+   *
+   * @param data The string data.
+   * @param charset The character set of the string. Defaults to UTF-8.
+   * @return The calculated [[MD5]]. */
+  def calculate(
+    data: String,
+    charset: Charset = StandardCharsets.UTF_8
+  ): MD5 =
+    calculate(data.getBytes(charset))
+
+  extension (md5: MD5)
+    /** @return
+      *   The underlying byte array.
+      */
+    def unwrap(): Array[Byte] = md5
+
+    /** @return
+      *   The underlying byte array.
+      */
+    def toBytes(): Array[Byte] = md5
+
+    /** Get the byte at the given index (0 to 15).
+      *
+      * Throws an exception if an out-of-bound index is given.
+      *
+      * @param index
+      *   The byte index (0 to 15).
+      * @return
+      *   The byte at the specified index.
+      */
+    def getByte(index: Int): Byte =
+      if index < 0 || index >= NumberOfBytes.unwrap() then
+        throw IndexOutOfBoundsException(
+          s"Index $index out of MD5 bound of $NumberOfBytes bytes."
+        )
+      else md5.apply(index)
+
+    /** Determine if this hash is the same as some other hash. Compares each
+      * byte in order.
+      *
+      * @param other
+      *   The [[MD5]] to compare against.
+      * @return
+      *   True if the hashes are identical, false otherwise.
+      */
+    def isSame(other: MD5): Boolean = md5.sameElements(other)
+
+    /** @return
+      *   This hash encoded to a Base64 string.
+      */
+    def base64(): EncodedString = Base64Encoder.encode(md5)
+
+    /** @return
+      *   This hash encoded to a Hexadecimal string.
+      */
+    def hex(): EncodedString = HexEncoder.encode(md5)
+
+end MD5
diff --git a/modules/core/src/main/scala/src/gs/std/v0/core/Nat.scala b/modules/core/src/main/scala/src/gs/std/v0/core/Nat.scala
new file mode 100644
index 0000000..d3a586c
--- /dev/null
+++ b/modules/core/src/main/scala/src/gs/std/v0/core/Nat.scala
@@ -0,0 +1,84 @@
+package gs.std.v0.core
+
+/** Opaque type for the natural numbers (including 0).
+  */
+opaque type Nat = Int
+
+/** Opaque type for the natural numbers (including 0).
+  */
+object Nat:
+
+  sealed trait Invalid
+  object Invalid extends Invalid
+
+  /** The number 0.
+    */
+  final val Zero: Nat = 0
+
+  /** The number 1.
+    */
+  final val One: Nat = 1
+
+  /** Express the given integer as a natural number.
+    *
+    * Throws an `IllegalArgumentException` if a negative value is given as
+    * input.
+    *
+    * @param value
+    *   The input integer.
+    * @return
+    *   The [[Nat]] instance.
+    */
+  def apply(value: Int): Nat =
+    if value >= 0 then value
+    else throw new IllegalArgumentException("Nat values must be 0 or greater.")
+
+  def validate(value: Int): Either[Invalid, Nat] =
+    if value >= 0 then Right(value) else Left(Invalid)
+
+  given CanEqual[Nat, Nat] = CanEqual.derived
+
+  given Ordering[Nat] with
+
+    /** @inheritDocs
+      */
+    def compare(
+      x: Nat,
+      y: Nat
+    ): Int = x - y
+
+  extension (nat: Nat)
+    /** @return
+      *   The underlying integer.
+      */
+    def unwrap(): Int = nat
+
+    /** @return
+      *   The next integer.
+      */
+    def next(): Nat = nat + 1
+
+    /** @return
+      *   The next integer.
+      */
+    def increment(): Nat = nat + 1
+
+    /** Add some natural number to this one.
+      *
+      * @param that
+      *   The number to add.
+      * @return
+      *   The sum of the numbers.
+      */
+    def +(that: Nat): Nat = nat + that
+
+    /** Multiply this natural number by some other natural number.
+      *
+      * @param that
+      *   The number to multiply by.
+      * @return
+      *   The product of the numbers.
+      */
+    def *(that: Nat): Nat = nat * that
+
+end Nat
diff --git a/modules/core/src/main/scala/src/gs/std/v0/core/SHA256.scala b/modules/core/src/main/scala/src/gs/std/v0/core/SHA256.scala
new file mode 100644
index 0000000..89fb61f
--- /dev/null
+++ b/modules/core/src/main/scala/src/gs/std/v0/core/SHA256.scala
@@ -0,0 +1,112 @@
+package gs.std.v0.core
+
+import java.nio.charset.Charset
+import java.nio.charset.StandardCharsets
+import java.security.MessageDigest
+
+/** Opaque type representing a SHA-256 hash.
+  */
+opaque type SHA256 = Array[Byte]
+
+/** Opaque type representing a SHA-256 hash.
+  */
+object SHA256:
+
+  /** SHA-256 hashes are exactly 32 bytes.
+    */
+  final val NumberOfBytes: ByteCount = ByteCount(32)
+
+  /** The algorithm name is "SHA-256".
+    */
+  final val Algorithm: String = "SHA-256"
+
+  /** Instantiate a [[SHA256]] from the given byte array. This function does not
+    * know whether the array is actually a calculated hash.
+    *
+    * Typically used for loading pre-validated hashes (e.g. from a database).
+    *
+    * @param bytes
+    *   The bytes - must contain exactly 32 bytes.
+    * @return
+    *   The new [[SHA256]] instance.
+    */
+  def fromBytes(bytes: Array[Byte]): SHA256 =
+    if NumberOfBytes.equal(bytes.length) then bytes
+    else
+      throw IllegalArgumentException(
+        s"SHA-256 values must be exactly $NumberOfBytes bytes."
+      )
+
+  /** Calculate the SHA-256 hash for the given byte array.
+    *
+    * @param data
+    *   The byte array.
+    * @return
+    *   The calculated [[SHA256]].
+    */
+  def calculate(data: Array[Byte]): SHA256 =
+    MessageDigest.getInstance(Algorithm).digest(data)
+
+  /** Calculate the SHA-256 hash for the given string.
+    *
+    * @param data
+    *   The string data.
+    * @param charset
+    *   The character set of the string. Defaults to UTF-8.
+    * @return
+    *   The calculated [[SHA256]].
+    */
+  def calculate(
+    data: String,
+    charset: Charset = StandardCharsets.UTF_8
+  ): SHA256 =
+    calculate(data.getBytes(charset))
+
+  extension (sha: SHA256)
+    /** @return
+      *   The underlying byte array.
+      */
+    def unwrap(): Array[Byte] = sha
+
+    /** @return
+      *   The underlying byte array.
+      */
+    def toBytes(): Array[Byte] = sha
+
+    /** Get the byte at the given index (0 to 31).
+      *
+      * Throws an exception if an out-of-bound index is given.
+      *
+      * @param index
+      *   The byte index (0 to 31).
+      * @return
+      *   The byte at the specified index.
+      */
+    def getByte(index: Int): Byte =
+      if index < 0 || index >= NumberOfBytes.unwrap() then
+        throw IndexOutOfBoundsException(
+          s"Index $index out of SHA-256 bound of $NumberOfBytes bytes."
+        )
+      else sha.apply(index)
+
+    /** Determine if this hash is the same as some other hash. Compares each
+      * byte in order.
+      *
+      * @param other
+      *   The [[SHA256]] to compare against.
+      * @return
+      *   True if the hashes are identical, false otherwise.
+      */
+    def isSame(other: SHA256): Boolean = sha.sameElements(other)
+
+    /** @return
+      *   This hash encoded to a Base64 string.
+      */
+    def base64(): EncodedString = Base64Encoder.encode(sha)
+
+    /** @return
+      *   This hash encoded to a Hexadecimal string.
+      */
+    def hex(): EncodedString = HexEncoder.encode(sha)
+
+end SHA256
diff --git a/modules/core/src/main/scala/src/gs/std/v0/core/Size.scala b/modules/core/src/main/scala/src/gs/std/v0/core/Size.scala
new file mode 100644
index 0000000..c00cbec
--- /dev/null
+++ b/modules/core/src/main/scala/src/gs/std/v0/core/Size.scala
@@ -0,0 +1,102 @@
+package gs.std.v0.core
+
+/** Opaque type for collection sizes. Values are guaranteed to be 0 or greater.
+  */
+opaque type Size = Int
+
+/** Opaque type for collection sizes. Values are guaranteed to be 0 or greater.
+  */
+object Size:
+
+  sealed trait Invalid
+  object Invalid extends Invalid
+
+  /** The size 0.
+    */
+  final val Zero: Size = 0
+
+  /** The size 1.
+    */
+  final val One: Size = 1
+
+  /** Express the given integer as a size.
+    *
+    * Throws an `IllegalArgumentException` if a negative value is given as
+    * input.
+    *
+    * @param value
+    *   The input integer.
+    * @return
+    *   The [[Size]] instance.
+    */
+  def apply(value: Int): Size =
+    if value >= 0 then value
+    else throw new IllegalArgumentException("Size values must be 0 or greater.")
+
+  def validate(value: Int): Either[Invalid, Size] =
+    if value >= 0 then Right(value) else Left(Invalid)
+
+  /** Express the size of any collection.
+    *
+    * @param iter
+    *   The collection.
+    * @return
+    *   The size of the collection.
+    */
+  def of(iter: Iterable[?]): Size = iter.size
+
+  /** Express the size of any array.
+    *
+    * @param arr
+    *   The array.
+    * @return
+    *   The size of the array.
+    */
+  def of(arr: Array[?]): Size = arr.length
+
+  given CanEqual[Size, Size] = CanEqual.derived
+
+  given Ordering[Size] with
+
+    /** @inheritDocs
+      */
+    def compare(
+      x: Size,
+      y: Size
+    ): Int = x - y
+
+  extension (size: Size)
+    /** @return
+      *   The underlying integer.
+      */
+    def unwrap(): Int = size
+
+    /** @return
+      *   The next value.
+      */
+    def next(): Size = size + 1
+
+    /** @return
+      *   The next value.
+      */
+    def increment(): Size = size + 1
+
+    /** Add some size to this one.
+      *
+      * @param that
+      *   The number to add.
+      * @return
+      *   The sum of the numbers.
+      */
+    def +(that: Size): Size = size + that
+
+    /** Multiply this size by some other size.
+      *
+      * @param that
+      *   The number to multiply by.
+      * @return
+      *   The product of the numbers.
+      */
+    def *(that: Size): Size = size * that
+
+end Size
diff --git a/modules/core/src/main/scala/src/gs/std/v0/core/UpdatedAt.scala b/modules/core/src/main/scala/src/gs/std/v0/core/UpdatedAt.scala
new file mode 100644
index 0000000..8244602
--- /dev/null
+++ b/modules/core/src/main/scala/src/gs/std/v0/core/UpdatedAt.scala
@@ -0,0 +1,37 @@
+package gs.std.v0.core
+
+import java.time.Instant
+
+/** Opaque type that represents the instant something was updated.
+  */
+opaque type UpdatedAt = Instant
+
+/** Opaque type that represents the instant something was updated.
+  */
+object UpdatedAt:
+
+  /** Instantiate a new [[UpdatedAt]] from the given `java.time.Instant`.
+    *
+    * @param value
+    *   The value to semantically represent.
+    * @return
+    *   The new [[UpdatedAt]].
+    */
+  def apply(value: Instant): UpdatedAt = value
+
+  given CanEqual[UpdatedAt, UpdatedAt] = CanEqual.derived
+
+  given Ordering[UpdatedAt] = Ordering[Instant]
+
+  extension (updatedAt: Instant)
+    /** @return
+      *   The underlying `java.time.Instant`.
+      */
+    def unwrap(): Instant = updatedAt
+
+    /** @return
+      *   The underlying `java.time.Instant`.
+      */
+    def toInstant(): Instant = updatedAt
+
+end UpdatedAt
diff --git a/modules/effect/src/main/scala/src/gs/std/v0/effect/ClockDateTimeProvider.scala b/modules/effect/src/main/scala/src/gs/std/v0/effect/ClockDateTimeProvider.scala
new file mode 100644
index 0000000..3074720
--- /dev/null
+++ b/modules/effect/src/main/scala/src/gs/std/v0/effect/ClockDateTimeProvider.scala
@@ -0,0 +1,87 @@
+package gs.std.v0.effect
+
+import cats.effect.Sync
+import cats.syntax.all.*
+import java.time.Clock
+import java.time.Instant
+import java.time.LocalDate
+import java.time.OffsetDateTime
+import java.time.ZonedDateTime
+import java.time.ZoneId
+
+/** Implementation of [[DateTimeProvider]] based on a specific
+  * `java.time.Clock`. All dates and times are calculated using this clock.
+  *
+  * @param clock
+  *   The clock used to calculate dates and times.
+  */
+final class ClockDateTimeProvider[F[_]: Sync](
+  val clock: Clock
+) extends DateTimeProvider[F]:
+
+  /** @inheritDocs
+    */
+  override def timestamp(): F[Instant] =
+    Sync[F].delay(Instant.now(clock))
+
+  /** @inheritDocs
+    */
+  override def nowInstant(): F[Instant] =
+    Sync[F].delay(Instant.now(clock))
+
+  /** @inheritDocs
+    */
+  override def nowZoned(): F[ZonedDateTime] =
+    Sync[F].delay(ZonedDateTime.now(clock))
+
+  /** @inheritDocs
+    */
+  override def nowOffset(): F[OffsetDateTime] =
+    Sync[F].delay(OffsetDateTime.now(clock))
+
+  /** @inheritDocs
+    */
+  override def today(): F[LocalDate] =
+    Sync[F].delay(LocalDate.now(clock))
+
+  /** @inheritDocs
+    */
+  override def yesterday(): F[LocalDate] =
+    today().map(_.minusDays(1L))
+
+  /** @inheritDocs
+    */
+  override def tomorrow(): F[LocalDate] =
+    today().map(_.plusDays(1L))
+
+object ClockDateTimeProvider:
+
+  /** Instantiate a new [[ClockDateTimeProvider]].
+    *
+    * @param clock
+    *   The clock to use for all date/time calculations.
+    * @return
+    *   The new [[DateTimeProvider]] instance.
+    */
+  def apply[F[_]: Sync](clock: Clock): DateTimeProvider[F] =
+    new ClockDateTimeProvider[F](clock)
+
+  /** @return
+    *   A new [[ClockDateTimeProvider]] based on the system's default zone using
+    *   the system's clock.
+    */
+  def system[F[_]: Sync]: DateTimeProvider[F] =
+    new ClockDateTimeProvider[F](Clock.systemDefaultZone())
+
+  /** Use a system clock aligned to the given zone.
+    *
+    * @param zoneId
+    *   The identifier of the zone to target.
+    * @return
+    *   A new [[ClockDateTimeProvider]] based on the specified zone using the
+    *   system's clock.
+    */
+  def forZone[F[_]: Sync](zoneId: ZoneId): DateTimeProvider[F] =
+    new ClockDateTimeProvider[F](Clock.system(zoneId))
+
+end ClockDateTimeProvider
diff --git a/modules/effect/src/main/scala/src/gs/std/v0/effect/DateTimeProvider.scala b/modules/effect/src/main/scala/src/gs/std/v0/effect/DateTimeProvider.scala
new file mode 100644
index 0000000..e95066b
--- /dev/null
+++ b/modules/effect/src/main/scala/src/gs/std/v0/effect/DateTimeProvider.scala
@@ -0,0 +1,44 @@
+package gs.std.v0.effect
+
+import java.time.Instant
+import java.time.LocalDate
+import java.time.OffsetDateTime
+import java.time.ZonedDateTime
+
+/** Provides date and time values.
+  */
+trait DateTimeProvider[F[_]]:
+  /** @return
+    *   The current timestamp (`java.time.Instant`).
+    */
+  def timestamp(): F[Instant]
+
+  /** @return
+    *   The current `java.time.Instant`.
+    */
+  def nowInstant(): F[Instant]
+
+  /** @return
+    *   The current date and time in the configured zone.
+    */
+  def nowZoned(): F[ZonedDateTime]
+
+  /** @return
+    *   The current date and time in the configured offset.
+    */
+  def nowOffset(): F[OffsetDateTime]
+
+  /** @return
+    *   The current date.
+    */
+  def today(): F[LocalDate]
+
+  /** @return
+    *   The date before today.
+    */
+  def yesterday(): F[LocalDate]
+
+  /** @return
+    *   The date after today.
+    */
+  def tomorrow(): F[LocalDate]
diff --git a/modules/effect/src/main/scala/src/gs/std/v0/effect/Rng.scala b/modules/effect/src/main/scala/src/gs/std/v0/effect/Rng.scala
new file mode 100644
index 0000000..813fce8
--- /dev/null
+++ b/modules/effect/src/main/scala/src/gs/std/v0/effect/Rng.scala
@@ -0,0 +1,388 @@
+package gs.std.v0.effect
+
+import cats.Applicative
+import cats.effect.Sync
+import cats.syntax.all.*
+import fs2.Stream
+import java.security.SecureRandom
+import java.util.Random
+
+/** Random number generator.
+  */
+trait Rng[F[_]]:
+
+  /** Explicitly set or update the seed using the given 8 bytes.
+    *
+    * @param seed
+    *   The seed value to assign or augment.
+    * @return
+    *   This [[Rng]] instance.
+    */
+  def updateSeed(seed: Long): F[Rng[F]]
+
+  /** @return
+    *   The next (unbounded) random `Int`.
+    */
+  def nextInt(): F[Int]
+
+  /** Calculate a number bounded inclusively within 0 and some bound.
+    *
+    * @param bound
+    *   The bound.
+    * @return
+    *   The calculated number.
+    */
+  def nextInt(bound: Int): F[Int]
+
+  /** Calculate a number bounded inclusively within some origin and some bound.
+    *
+    * @param origin
+    *   The origin.
+    * @param bound
+    *   The bound.
+    * @return
+    *   The calculated number.
+    */
+  def nextInt(
+    origin: Int,
+    bound: Int
+  ): F[Int]
+
+  /** @return
+    *   The next (unbounded) random `Long`.
+    */
+  def nextLong(): F[Long]
+
+  /** Calculate a number bounded inclusively within 0 and some bound.
+    *
+    * @param bound
+    *   The bound.
+    * @return
+    *   The calculated number.
+    */
+  def nextLong(bound: Long): F[Long]
+
+  /** Calculate a number bounded inclusively within some origin and some bound.
+    *
+    * @param origin
+    *   The origin.
+    * @param bound
+    *   The bound.
+    * @return
+    *   The calculated number.
+    */
+  def nextLong(
+    origin: Long,
+    bound: Long
+  ): F[Long]
+
+  /** @return
+    *   The next (unbounded) random `Double`.
+    */
+  def nextDouble(): F[Double]
+
+  /** Calculate a number bounded inclusively within 0 and some bound.
+    *
+    * @param bound
+    *   The bound.
+    * @return
+    *   The calculated number.
+    */
+  def nextDouble(bound: Double): F[Double]
+
+  /** Calculate a number bounded inclusively within some origin and some bound.
+    *
+    * @param origin
+    *   The origin.
+    * @param bound
+    *   The bound.
+    * @return
+    *   The calculated number.
+    */
+  def nextDouble(
+    origin: Double,
+    bound: Double
+  ): F[Double]
+
+  /** @return
+    *   The next randomly selected `true` or `false` value.
+    */
+  def nextBoolean(): F[Boolean]
+
+  /** Produce an infinite stream of `Int` bounded inclusively within some origin
+    * and some bound.
+    *
+    * @param origin
+    *   The origin.
+    * @param bound
+    *   The bound.
+    * @return
+    *   The infinite stream of values.
+    */
+  def nextInts(
+    origin: Int,
+    bound: Int
+  ): Stream[F, Int]
+
+  /** Produce an infinite stream of `Long` bounded inclusively within some
+    * origin and some bound.
+    *
+    * @param origin
+    *   The origin.
+    * @param bound
+    *   The bound.
+    * @return
+    *   The infinite stream of values.
+    */
+  def nextLongs(
+    origin: Long,
+    bound: Long
+  ): Stream[F, Long]
+
+  /** Produce an infinite stream of `Double` bounded inclusively within some
+    * origin and some bound.
+    *
+    * @param origin
+    *   The origin.
+    * @param bound
+    *   The bound.
+    * @return
+    *   The infinite stream of values.
+    */
+  def nextDoubles(
+    origin: Double,
+    bound: Double
+  ): Stream[F, Double]
+
+object Rng:
+
+  /** Instantiate [[Rng]] using a new `java.util.Random` instance.
+    *
+    * For secure random number generation, please refer to the `secure[F]`
+    * function.
+    *
+    * @param random
+    *   The `java.util.Random` instance.
+    * @return
+    *   The new [[Rng]].
+    */
+  def default[F[_]: Sync]: Rng[F] =
+    default[F](new Random())
+
+  /** Instantiate [[Rng]] using the given random number generator.
+    *
+    * @param random
+    *   The `java.util.Random` instance.
+    * @return
+    *   The new [[Rng]].
+    */
+  def default[F[_]: Sync](random: Random): Rng[F] =
+    new JavaRandom[F](random)
+
+  /** Instantiate [[Rng]] using a new `java.security.SecureRandom` instance.
+    *
+    * @param random
+    *   The `java.security.SecureRandom` instance.
+    * @return
+    *   The new [[Rng]].
+    */
+  def secure[F[_]: Sync]: Rng[F] =
+    secure[F](new SecureRandom())
+
+  /** Instantiate [[Rng]] using the given secure random number generator.
+    *
+    * @param random
+    *   The `java.security.SecureRandom` instance.
+    * @return
+    *   The new [[Rng]].
+    */
+  def secure[F[_]: Sync](random: SecureRandom): Rng[F] =
+    new JavaRandom[F](random)
+
+  /** @return
+    *   New instance of [[Rng]] that always returns `0` or `false`.
+    */
+  def zero[F[_]: Applicative]: Rng[F] =
+    new Zero[F]
+
+  /** Implementation of [[Rng]] based on any given `java.util.Random` instance.
+    *
+    * @param random
+    *   The underlying random number generator.
+    */
+  final class JavaRandom[F[_]: Sync](random: Random) extends Rng[F]:
+
+    /** @inheritDocs
+      */
+    override def updateSeed(seed: Long): F[Rng[F]] =
+      Sync[F].delay(random.setSeed(seed)).as(this)
+
+    /** @inheritDocs
+      */
+    override def nextInt(): F[Int] =
+      Sync[F].delay(random.nextInt())
+
+    /** @inheritDocs
+      */
+    override def nextInt(bound: Int): F[Int] =
+      Sync[F].delay(random.nextInt(bound))
+
+    /** @inheritDocs
+      */
+    override def nextInt(
+      origin: Int,
+      bound: Int
+    ): F[Int] =
+      Sync[F].delay(random.nextInt(origin, bound))
+
+    /** @inheritDocs
+      */
+    override def nextLong(): F[Long] =
+      Sync[F].delay(random.nextLong())
+
+    /** @inheritDocs
+      */
+    override def nextLong(bound: Long): F[Long] =
+      Sync[F].delay(random.nextLong(bound))
+
+    /** @inheritDocs
+      */
+    override def nextLong(
+      origin: Long,
+      bound: Long
+    ): F[Long] =
+      Sync[F].delay(random.nextLong(origin, bound))
+
+    /** @inheritDocs
+      */
+    override def nextDouble(): F[Double] =
+      Sync[F].delay(random.nextDouble())
+
+    /** @inheritDocs
+      */
+    override def nextDouble(bound: Double): F[Double] =
+      Sync[F].delay(random.nextDouble(bound))
+
+    /** @inheritDocs
+      */
+    override def nextDouble(
+      origin: Double,
+      bound: Double
+    ): F[Double] =
+      Sync[F].delay(random.nextDouble(origin, bound))
+
+    /** @inheritDocs
+      */
+    override def nextBoolean(): F[Boolean] =
+      Sync[F].delay(random.nextBoolean())
+
+    /** @inheritDocs
+      */
+    override def nextInts(
+      origin: Int,
+      bound: Int
+    ): Stream[F, Int] =
+      Stream.repeatEval(nextInt(origin, bound))
+
+    /** @inheritDocs
+      */
+    override def nextLongs(
+      origin: Long,
+      bound: Long
+    ): Stream[F, Long] =
+      Stream.repeatEval(nextLong(origin, bound))
+
+    /** @inheritDocs
+      */
+    override def nextDoubles(
+      origin: Double,
+      bound: Double
+    ): Stream[F, Double] =
+      Stream.repeatEval(nextDouble(origin, bound))
+
+  end JavaRandom
+
+  /** Implementation of [[Rng]] that always returns `0` or `false`.
+    */
+  final class Zero[F[_]: Applicative] extends Rng[F]:
+
+    /** @inheritDocs
+      */
+    override def updateSeed(seed: Long): F[Rng[F]] = Applicative[F].pure(this)
+
+    /** @inheritDocs
+      */
+    override def nextInt(): F[Int] = Applicative[F].pure(0)
+
+    /** @inheritDocs
+      */
+    override def nextInt(bound: Int): F[Int] = Applicative[F].pure(0)
+
+    /** @inheritDocs
+      */
+    override def nextInt(
+      origin: Int,
+      bound: Int
+    ): F[Int] = Applicative[F].pure(0)
+
+    /** @inheritDocs
+      */
+    override def nextLong(): F[Long] = Applicative[F].pure(0)
+
+    /** @inheritDocs
+      */
+    override def nextLong(bound: Long): F[Long] = Applicative[F].pure(0)
+
+    /** @inheritDocs
+      */
+    override def nextLong(
+      origin: Long,
+      bound: Long
+    ): F[Long] = Applicative[F].pure(0)
+
+    /** @inheritDocs
+      */
+    override def nextDouble(): F[Double] = Applicative[F].pure(0.0)
+
+    /** @inheritDocs
+      */
+    override def nextDouble(bound: Double): F[Double] = Applicative[F].pure(0.0)
+
+    /** @inheritDocs
+      */
+    override def nextDouble(
+      origin: Double,
+      bound: Double
+    ): F[Double] = Applicative[F].pure(0.0)
+
+    /** @inheritDocs
+      */
+    override def nextBoolean(): F[Boolean] = Applicative[F].pure(false)
+
+    /** @inheritDocs
+      */
+    override def nextInts(
+      origin: Int,
+      bound: Int
+    ): Stream[F, Int] =
+      Stream.repeatEval(Applicative[F].pure(0))
+
+    /** @inheritDocs
+      */
+    override def nextLongs(
+      origin: Long,
+      bound: Long
+    ): Stream[F, Long] =
+      Stream.repeatEval(Applicative[F].pure(0))
+
+    /** @inheritDocs
+      */
+    override def nextDoubles(
+      origin: Double,
+      bound: Double
+    ): Stream[F, Double] =
+      Stream.repeatEval(Applicative[F].pure(0.0))
+
+  end Zero
+
+end Rng
diff --git a/modules/effect/src/test/resources/sha256-input b/modules/effect/src/test/resources/sha256-input
new file mode 100644
index 0000000..9fd0447
Binary files /dev/null and b/modules/effect/src/test/resources/sha256-input differ
diff --git a/modules/io/src/main/scala/src/gs/std/v0/io/Files.scala b/modules/io/src/main/scala/src/gs/std/v0/io/Files.scala
new file mode 100644
index 0000000..8b7c6bd
--- /dev/null
+++ b/modules/io/src/main/scala/src/gs/std/v0/io/Files.scala
@@ -0,0 +1,118 @@
+package gs.std.v0.io
+
+import cats.effect.Resource
+import cats.effect.Sync
+import java.io.InputStream
+import java.io.OutputStream
+import java.nio.charset.Charset
+import java.nio.charset.StandardCharsets
+import java.nio.file.OpenOption
+import java.nio.file.Path
+import java.nio.file.StandardOpenOption
+import scala.jdk.CollectionConverters.*
+
+/** Common operations on files.
+  *
+  * Includes wrappers around some `java.nio.file.Files` functionality.
+  *
+  * For streaming operations, just use the `fs2.io` library.
+  */
+object Files:
+
+  def readFileAsString[F[_]: Sync](
+    path: Path,
+    charset: Charset = StandardCharsets.UTF_8
+  ): F[String] =
+    Sync[F].delay(java.nio.file.Files.readString(path, charset))
+
+  def readFileAsBytes[F[_]: Sync](path: Path): F[Array[Byte]] =
+    Sync[F].delay(java.nio.file.Files.readAllBytes(path))
+
+  def readFileAsLines[F[_]: Sync](
+    path: Path,
+    charset: Charset = StandardCharsets.UTF_8
+  ): F[List[String]] =
+    Sync[F].delay(
+      java.nio.file.Files.readAllLines(path, charset).asScala.toList
+    )
+
+  def overwriteFileWithString[F[_]: Sync](
+    path: Path,
+    data: String
+  ): F[Unit] =
+    Sync[F].delay(
+      java.nio.file.Files.writeString(
+        path,
+        data,
+        StandardOpenOption.WRITE,
+        StandardOpenOption.TRUNCATE_EXISTING
+      )
+    )
+
+  def overwriteFileWithBytes[F[_]: Sync](
+    path: Path,
+    data: Array[Byte]
+  ): F[Unit] =
+    Sync[F].delay(
+      java.nio.file.Files.write(
+        path,
+        data,
+        StandardOpenOption.WRITE,
+        StandardOpenOption.TRUNCATE_EXISTING
+      )
+    )
+
+  def appendFileWithString[F[_]: Sync](
+    path: Path,
+    data: String
+  ): F[Unit] =
+    Sync[F].delay(
+      java.nio.file.Files.writeString(
+        path,
+        data,
+        StandardOpenOption.WRITE,
+        StandardOpenOption.APPEND
+      )
+    )
+
+  def appendFileWithBytes[F[_]: Sync](
+    path: Path,
+    data: Array[Byte]
+  ): F[Unit] =
+    Sync[F].delay(
+      java.nio.file.Files
+        .write(path, data, StandardOpenOption.WRITE, StandardOpenOption.APPEND)
+    )
+
+  def isRegularFile[F[_]: Sync](path: Path): F[Boolean] =
+    Sync[F].delay(java.nio.file.Files.isRegularFile(path))
+
+  def isReadable[F[_]: Sync](path: Path): F[Boolean] =
+    Sync[F].delay(java.nio.file.Files.isReadable(path))
+
+  def isWritable[F[_]: Sync](path: Path): F[Boolean] =
+    Sync[F].delay(java.nio.file.Files.isWritable(path))
+
+  def isDirectory[F[_]: Sync](path: Path): F[Boolean] =
+    Sync[F].delay(java.nio.file.Files.isDirectory(path))
+
+  def isExecutable[F[_]: Sync](path: Path): F[Boolean] =
+    Sync[F].delay(java.nio.file.Files.isExecutable(path))
+
+  def openInputStream[F[_]: Sync](
+    path: Path,
+    openOptions: OpenOption*
+  ): Resource[F, InputStream] =
+    Resource.make(
+      Sync[F].delay(java.nio.file.Files.newInputStream(path, openOptions*))
+    )(inputStream => Sync[F].delay(inputStream.close()))
+
+  def openOutputStream[F[_]: Sync](
+    path: Path,
+    openOptions: OpenOption*
+  ): Resource[F, OutputStream] =
+    Resource.make(
+      Sync[F].delay(java.nio.file.Files.newOutputStream(path, openOptions*))
+    )(outputStream => Sync[F].delay(outputStream.close()))
+
+end Files
diff --git a/src/main/scala/gs/std/v0/Blob.scala b/src/main/scala/gs/std/v0/Blob.scala
deleted file mode 100644
index d18a759..0000000
--- a/src/main/scala/gs/std/v0/Blob.scala
+++ /dev/null
@@ -1,44 +0,0 @@
-package gs.std.v0
-
-import java.util.Base64
-
-/**
-  * Represents a blob -- some array of bytes.
-  *
-  * @param data The underlying data.
-  */
-final class Blob(private val data: Array[Byte]) extends IndexedSeq[Byte]:
-
-  /** @inheritDocs */
-  override def apply(i: Int): Byte = byteAt(i)
-
-  /** @inheritDocs */
-  override def length: Int = data.length
-
-  /**
-   * @return The number of bytes in this blob, expressed as a count.
-   */
-  def numberOfBytes: ByteCount = ByteCount(data.length)
-
-  /** @inheritDocs */
-  override def equals(obj: Any): Boolean = 
-    obj match
-      case other: Blob => data.sameElements(other.data)
-      case other: Array[Byte] => data.sameElements(other)
-      case _ => false
-
-  /** @inheritDocs */
-  override def hashCode(): Int = data.hashCode()
-
-  /**
-   * Retrieve the byte at the given index.
-   *
-   * @param index The index.
-   * @return The byte stored at the given index.
-   */
-  def byteAt(index: Int): Byte = data.apply(index)
-
-  /**
-   * @return This byte array, encoded as a base64 string.
-   */
-  def base64(): String = Base64.getEncoder().encodeToString(data)
diff --git a/src/main/scala/gs/std/v0/ByteCount.scala b/src/main/scala/gs/std/v0/ByteCount.scala
deleted file mode 100644
index 8a95565..0000000
--- a/src/main/scala/gs/std/v0/ByteCount.scala
+++ /dev/null
@@ -1,132 +0,0 @@
-package gs.std.v0
-
-/**
-   * Opaque type for some number of bytes (>= 0).
-  */
-opaque type ByteCount = Long
-
-/**
-   * Opaque type for some number of bytes (>= 0).
-  */
-object ByteCount:
-
-  /**
-   * 0 bytes.
-   */
-  final val Zero: ByteCount = 0
-
-  /**
-   * 1,000 bytes.
-   */
-  final val OneKilobyte: ByteCount = 1000
-
-  /**
-   * 1,000,000 bytes.
-   */
-  final val OneMegabyte: ByteCount = 1000000
-
-  /**
-   * 1,000,000,000 bytes.
-   */
-  final val OneGigabyte: ByteCount = 1000000000
-
-  /**
-   * Express the given number as a byte count. All values are normalized to the
-   * absolute value -- negative values are coerced to positive.
-   *
-   * @param value The input integer.
-   * @return The [[ByteCount]] instance.
-   */
-  def apply(value: Long): ByteCount = Math.abs(value)
-
-  /**
-   * 1 kilobyte = 1,000 bytes
-   *
-   * @param kb The number of kilobytes.
-   * @return The number of bytes.
-   */
-  def fromKilobytes(kb: Long): ByteCount =
-    Math.abs(kb) * 1000L
-
-  /**
-   * 1 megabyte = 1,000,000 bytes
-   *
-   * @param mb The number of megabytes.
-   * @return The number of bytes.
-   */
-  def fromMegabytes(mb: Long): ByteCount =
-    Math.abs(mb) * 1000000L
-
-  /**
-   * 1 gigabyte = 1,000,000,000 bytes
-   *
-   * @param mb The number of gigabytes.
-   * @return The number of bytes.
-   */
-  def fromGigabytes(gb: Long): ByteCount =
-    Math.abs(gb) * 1000000000
-
-  given CanEqual[ByteCount, ByteCount] = CanEqual.derived
-
-  given Ordering[ByteCount] with
-    /** @inheritDocs */
-    def compare(x: ByteCount, y: ByteCount): Int = 
-      if x > y then 1 else if x == y then 0 else -1
-
-  extension (byteCount: ByteCount)
-    /**
-     * @return The underlying `Long`.
-     */
-    def unwrap(): Long = byteCount
-
-    /**
-     * @return The underlying `Long`.
-     */
-    def toLong(): Long = byteCount
-
-    /**
-     * 1 kilobyte = 1,000 bytes
-     *
-     * @return The number of kilobytes represented by this count.
-     */
-    def toKilobytes(): Double = byteCount / 1000.0
-
-    /**
-     * 1 megabyte = 1,000,000 bytes.
-     *
-     * @return The number of megabytes represented by this count.
-     */
-    def toMegabytes(): Double = byteCount / 1000000.0
-
-    /**
-     * 1 gigabyte = 1,000,000,000 bytes.
-     *
-     * @return The number of gigabytes represented by this count.
-     */
-    def toGigabytes(): Double = byteCount / 1000000000.0
-
-    /**
-     * Add some count to this one.
-     *
-     * @param that The number to add.
-     * @return The sum of the numbers.
-     */
-    def +(that: ByteCount): ByteCount = byteCount + that
-
-    /**
-     * Multiply this count by some other count.
-     *
-     * @param that The number to multiply by.
-     * @return The product of the numbers.
-     */
-    def *(that: ByteCount): ByteCount = byteCount * that
-
-    /**
-     * Check if this value is the same as some number.
-     *
-     * @param value The number to compare against.
-     * @return True if the values are equal, false otherwise.
-     */
-    def equal(value: Int): Boolean = byteCount == value.toLong
-
-end ByteCount
diff --git a/src/main/scala/gs/std/v0/CreatedAt.scala b/src/main/scala/gs/std/v0/CreatedAt.scala
deleted file mode 100644
index 4e47dcc..0000000
--- a/src/main/scala/gs/std/v0/CreatedAt.scala
+++ /dev/null
@@ -1,38 +0,0 @@
-package gs.std.v0
-
-import java.time.Instant
-
-/**
-  * Opaque type that represents the instant something was created.
-  */
-opaque type CreatedAt = Instant
-
-/**
-  * Opaque type that represents the instant something was created.
-  */
-object CreatedAt:
-
-  /**
-   * Instantiate a new [[CreatedAt]] from the given `java.time.Instant`.
-   *
-   * @param value The value to semantically represent.
-   * @return The new [[CreatedAt]].
-   */
-  def apply(value: Instant): CreatedAt = value
-
-  given CanEqual[CreatedAt, CreatedAt] = CanEqual.derived
-
-  given Ordering[CreatedAt] = Ordering[Instant]
-
-  extension (createdAt: Instant)
-    /**
-     * @return The underlying `java.time.Instant`.
-     */
-    def unwrap(): Instant = createdAt
-
-    /**
-     * @return The underlying `java.time.Instant`.
-     */
-    def toInstant(): Instant = createdAt
-
-end CreatedAt
diff --git a/src/main/scala/gs/std/v0/Decoder.scala b/src/main/scala/gs/std/v0/Decoder.scala
deleted file mode 100644
index 2570ab8..0000000
--- a/src/main/scala/gs/std/v0/Decoder.scala
+++ /dev/null
@@ -1,13 +0,0 @@
-package gs.std.v0
-
-/**
-  * Interface for byte decoding from encoded String formats.
-  */
-trait Decoder[-A <: EncodedString]:
-  /**
-   * Decode an input string to an array of bytes.
-   *
-   * @param input The input to decode.
-   * @return The decoded byte array.
-   */
-  def decode(input: A): Array[Byte]
diff --git a/src/main/scala/gs/std/v0/MD5.scala b/src/main/scala/gs/std/v0/MD5.scala
deleted file mode 100644
index fbe5f60..0000000
--- a/src/main/scala/gs/std/v0/MD5.scala
+++ /dev/null
@@ -1,105 +0,0 @@
-package gs.std.v0
-
-import java.security.MessageDigest
-import java.nio.charset.Charset
-import java.nio.charset.StandardCharsets
-
-/**
-  * Opaque type representing a MD5 hash.
-  */
-opaque type MD5 = Array[Byte]
-
-/**
-  * Opaque type representing a MD5 hash.
-  */
-object MD5:
-
-  /**
-   * MD5 hashes are exactly 16 bytes.
-   */
-  final val NumberOfBytes: ByteCount = ByteCount(16)
-
-  /**
-   * The algorithm name is "MD5".
-   */
-  final val Algorithm: String = "MD5"
-
-  /**
-   * Instantiate a [[MD5]] from the given byte array. This function does not
-   * know whether the array is actually a calculated hash.
-   *
-   * Typically used for loading pre-validated hashes (e.g. from a database).
-   *
-   * @param bytes The bytes - must contain exactly 16 bytes.
-   * @return The new [[MD5]] instance.
-   */
-  def fromBytes(bytes: Array[Byte]): MD5 = 
-    if NumberOfBytes.equal(bytes.length) then
-      bytes
-    else
-      throw IllegalArgumentException(s"MD5 values must be exactly $NumberOfBytes bytes.")
-
-  /**
-   * Calculate the MD5 hash for the given byte array.
-   *
-   * @param data The byte array.
-   * @return The calculated [[MD5]].
-   */
-  def calculate(data: Array[Byte]): MD5 = 
-    MessageDigest.getInstance(Algorithm).digest(data)
-
-  /*
-   * Calculate the MD5 hash for the given string.
-   *
-   * @param data The string data.
-   * @param charset The character set of the string. Defaults to UTF-8.
-   * @return The calculated [[MD5]].
-   */
-  def calculate(data: String, charset: Charset = StandardCharsets.UTF_8): MD5 =
-    calculate(data.getBytes(charset))
-
-  extension (md5: MD5)
-    /**
-     * @return The underlying byte array.
-     */
-    def unwrap(): Array[Byte] = md5
-
-    /**
-     * @return The underlying byte array.
-     */
-    def toBytes(): Array[Byte] = md5
-
-    /**
-     * Get the byte at the given index (0 to 15).
-     *
-     * Throws an exception if an out-of-bound index is given.
-     *
-     * @param index The byte index (0 to 15).
-     * @return The byte at the specified index.
-     */
-    def getByte(index: Int): Byte =
-      if index < 0 || index >= NumberOfBytes.unwrap() then
-        throw IndexOutOfBoundsException(s"Index $index out of MD5 bound of $NumberOfBytes bytes.")
-      else
-        md5.apply(index)
-
-    /**
-     * Determine if this hash is the same as some other hash. Compares each byte
-     * in order.
-     *
-     * @param other The [[MD5]] to compare against.
-     * @return True if the hashes are identical, false otherwise.
-     */
-    def isSame(other: MD5): Boolean = md5.sameElements(other)
-
-    /**
-     * @return This hash encoded to a Base64 string.
-     */
-    def base64(): EncodedString = Base64Encoder.encode(md5)
-
-    /**
-     * @return This hash encoded to a Hexadecimal string.
-     */
-    def hex(): EncodedString = HexEncoder.encode(md5)
-
-end MD5
diff --git a/src/main/scala/gs/std/v0/Nat.scala b/src/main/scala/gs/std/v0/Nat.scala
deleted file mode 100644
index 07b5d78..0000000
--- a/src/main/scala/gs/std/v0/Nat.scala
+++ /dev/null
@@ -1,81 +0,0 @@
-package gs.std.v0
-
-/**
-  * Opaque type for the natural numbers (including 0).
-  */
-opaque type Nat = Int
-
-/**
-  * Opaque type for the natural numbers (including 0).
-  */
-object Nat:
-
-  sealed trait Invalid
-  object Invalid extends Invalid
-
-  /**
-   * The number 0.
-   */
-  final val Zero: Nat = 0
-
-  /**
-   * The number 1.
-   */
-  final val One: Nat = 1
-
-  /**
-   * Express the given integer as a natural number.
-   *
-   * Throws an `IllegalArgumentException` if a negative value is given as input.
-   *
-   * @param value The input integer.
-   * @return The [[Nat]] instance.
-   */
-  def apply(value: Int): Nat =
-    if value >= 0 then
-      value
-    else
-      throw new IllegalArgumentException("Nat values must be 0 or greater.")
-
-  def validate(value: Int): Either[Invalid, Nat] =
-    if value >= 0 then Right(value) else Left(Invalid)
-
-  given CanEqual[Nat, Nat] = CanEqual.derived
-
-  given Ordering[Nat] with
-    /** @inheritDocs */
-    def compare(x: Nat, y: Nat): Int = x - y
-
-  extension (nat: Nat)
-    /**
-     * @return The underlying integer.
-     */
-    def unwrap(): Int = nat
-
-    /**
-     * @return The next integer.
-     */
-    def next(): Nat = nat + 1
-
-    /**
-     * @return The next integer.
-     */
-    def increment(): Nat = nat + 1
-
-    /**
-     * Add some natural number to this one.
-     *
-     * @param that The number to add.
-     * @return The sum of the numbers.
-     */
-    def +(that: Nat): Nat = nat + that
-
-    /**
-     * Multiply this natural number by some other natural number.
-     *
-     * @param that The number to multiply by.
-     * @return The product of the numbers.
-     */
-    def *(that: Nat): Nat = nat * that
-
-end Nat
diff --git a/src/main/scala/gs/std/v0/SHA256.scala b/src/main/scala/gs/std/v0/SHA256.scala
deleted file mode 100644
index c14df04..0000000
--- a/src/main/scala/gs/std/v0/SHA256.scala
+++ /dev/null
@@ -1,105 +0,0 @@
-package gs.std.v0
-
-import java.security.MessageDigest
-import java.nio.charset.Charset
-import java.nio.charset.StandardCharsets
-
-/**
-  * Opaque type representing a SHA-256 hash.
-  */
-opaque type SHA256 = Array[Byte]
-
-/**
-  * Opaque type representing a SHA-256 hash.
-  */
-object SHA256:
-
-  /**
-   * SHA-256 hashes are exactly 32 bytes.
-   */
-  final val NumberOfBytes: ByteCount = ByteCount(32)
-
-  /**
-   * The algorithm name is "SHA-256".
-   */
-  final val Algorithm: String = "SHA-256"
-
-  /**
-   * Instantiate a [[SHA256]] from the given byte array. This function does not
-   * know whether the array is actually a calculated hash.
-   *
-   * Typically used for loading pre-validated hashes (e.g. from a database).
-   *
-   * @param bytes The bytes - must contain exactly 32 bytes.
-   * @return The new [[SHA256]] instance.
-   */
-  def fromBytes(bytes: Array[Byte]): SHA256 = 
-    if NumberOfBytes.equal(bytes.length) then
-      bytes
-    else
-      throw IllegalArgumentException(s"SHA-256 values must be exactly $NumberOfBytes bytes.")
-
-  /**
-   * Calculate the SHA-256 hash for the given byte array.
-   *
-   * @param data The byte array.
-   * @return The calculated [[SHA256]].
-   */
-  def calculate(data: Array[Byte]): SHA256 = 
-    MessageDigest.getInstance(Algorithm).digest(data)
-
-  /**
-   * Calculate the SHA-256 hash for the given string.
-   *
-   * @param data The string data.
-   * @param charset The character set of the string. Defaults to UTF-8.
-   * @return The calculated [[SHA256]].
-   */
-  def calculate(data: String, charset: Charset = StandardCharsets.UTF_8): SHA256 =
-    calculate(data.getBytes(charset))
-
-  extension (sha: SHA256)
-    /**
-     * @return The underlying byte array.
-     */
-    def unwrap(): Array[Byte] = sha
-
-    /**
-     * @return The underlying byte array.
-     */
-    def toBytes(): Array[Byte] = sha
-
-    /**
-     * Get the byte at the given index (0 to 31).
-     *
-     * Throws an exception if an out-of-bound index is given.
-     *
-     * @param index The byte index (0 to 31).
-     * @return The byte at the specified index.
-     */
-    def getByte(index: Int): Byte =
-      if index < 0 || index >= NumberOfBytes.unwrap() then
-        throw IndexOutOfBoundsException(s"Index $index out of SHA-256 bound of $NumberOfBytes bytes.")
-      else
-        sha.apply(index)
-
-    /**
-     * Determine if this hash is the same as some other hash. Compares each byte
-     * in order.
-     *
-     * @param other The [[SHA256]] to compare against.
-     * @return True if the hashes are identical, false otherwise.
-     */
-    def isSame(other: SHA256): Boolean = sha.sameElements(other)
-
-    /**
-     * @return This hash encoded to a Base64 string.
-     */
-    def base64(): EncodedString = Base64Encoder.encode(sha)
-
-    /**
-     * @return This hash encoded to a Hexadecimal string.
-     */
-    def hex(): EncodedString = HexEncoder.encode(sha)
-
-end SHA256
diff --git a/src/main/scala/gs/std/v0/Size.scala b/src/main/scala/gs/std/v0/Size.scala
deleted file mode 100644
index 0de45fa..0000000
--- a/src/main/scala/gs/std/v0/Size.scala
+++ /dev/null
@@ -1,97 +0,0 @@
-package gs.std.v0
-
-/**
-  * Opaque type for collection sizes. Values are guaranteed to be 0 or greater.
-  */
-opaque type Size = Int
-
-/**
-  * Opaque type for collection sizes. Values are guaranteed to be 0 or greater.
-  */
-object Size:
-
-  sealed trait Invalid
-  object Invalid extends Invalid
-
-  /**
-   * The size 0.
-   */
-  final val Zero: Size = 0
-
-  /**
-   * The size 1.
-   */
-  final val One: Size = 1
-
-  /**
-   * Express the given integer as a size.
-   *
-   * Throws an `IllegalArgumentException` if a negative value is given as input.
-   *
-   * @param value The input integer.
-   * @return The [[Size]] instance.
-   */
-  def apply(value: Int): Size =
-    if value >= 0 then
-      value
-    else
-      throw new IllegalArgumentException("Size values must be 0 or greater.")
-
-  def validate(value: Int): Either[Invalid, Size] =
-    if value >= 0 then Right(value) else Left(Invalid)
-
-  /**
-   * Express the size of any collection.
-   *
-   * @param iter The collection.
-   * @return The size of the collection.
-   */
-  def of(iter: Iterable[?]): Size = iter.size
-
-  /**
-   * Express the size of any array.
-   *
-   * @param arr The array.
-   * @return The size of the array.
-   */
-  def of(arr: Array[?]): Size = arr.length
-
-  given CanEqual[Size, Size] = CanEqual.derived
-
-  given Ordering[Size] with
-    /** @inheritDocs */
-    def compare(x: Size, y: Size): Int = x - y
-
-  extension (size: Size)
-    /**
-     * @return The underlying integer.
-     */
-    def unwrap(): Int = size
-
-    /**
-     * @return The next value.
-     */
-    def next(): Size = size + 1
-
-    /**
-     * @return The next value.
-     */
-    def increment(): Size = size + 1
-
-    /**
-     * Add some size to this one.
-     *
-     * @param that The number to add.
-     * @return The sum of the numbers.
-     */
-    def +(that: Size): Size = size + that
-
-    /**
-     * Multiply this size by some other size.
-     *
-     * @param that The number to multiply by.
-     * @return The product of the numbers.
-     */
-    def *(that: Size): Size = size * that
-
-end Size
diff --git a/src/main/scala/gs/std/v0/UpdatedAt.scala b/src/main/scala/gs/std/v0/UpdatedAt.scala
deleted file mode 100644
index cf32ef8..0000000
--- a/src/main/scala/gs/std/v0/UpdatedAt.scala
+++ /dev/null
@@ -1,39 +0,0 @@
-package gs.std.v0
-
-import java.time.Instant
-
-/**
-  * Opaque type that represents the instant something was updated.
-  */
-opaque type UpdatedAt = Instant
-
-/**
-  * Opaque type that represents the instant something was updated.
-  */
-object UpdatedAt:
-
-  /**
-   * Instantiate a new [[UpdatedAt]] from the given `java.time.Instant`.
-   *
-   * @param value The value to semantically represent.
-   * @return The new [[UpdatedAt]].
-   */
-  def apply(value: Instant): UpdatedAt = value
-
-  given CanEqual[UpdatedAt, UpdatedAt] = CanEqual.derived
-
-  given Ordering[UpdatedAt] = Ordering[Instant]
-
-  extension (updatedAt: Instant)
-    /**
-     * @return The underlying `java.time.Instant`.
-     */
-    def unwrap(): Instant = updatedAt
-
-    /**
-     * @return The underlying `java.time.Instant`.
-     */
-    def toInstant(): Instant = updatedAt
-
-end UpdatedAt
-