diff --git a/.github/workflows/dart.yml b/.github/workflows/dart.yml
new file mode 100644
index 0000000..fec8bc5
--- /dev/null
+++ b/.github/workflows/dart.yml
@@ -0,0 +1,25 @@
+name: Dart
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  test:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+        channel: [stable, beta, dev]
+    steps:
+      - uses: actions/checkout@v2
+      - uses: ./
+        with:
+          channel: ${{ matrix.channel }}
+
+      - name: Run hello world
+        run: |
+          echo "main() { print('hello world'); }" > hello.dart
+          dart hello.dart
diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
index 0000000..da776a9
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,4 @@
+## Initial version
+
+- Basic download and setup.
+- Support for Linux, macOS, and Windows.
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..b9cb482
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,26 @@
+Copyright 2020, the Dart project authors. All rights reserved.
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+    * Neither the name of Google Inc. nor the names of its
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
\ No newline at end of file
diff --git a/README.md b/README.md
index f00249f..daa9274 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,102 @@
 # setup-dart
-GitHub Action for install and setup of a Dart SDK
+
+This [GitHub Action]() installs and sets up of a Dart SDK for use in actions by:
+
+* Downloading the Dart SDK
+* Adding the `dart` command and `pub` cache to path
+
+# Usage
+
+## Basic
+
+Install the latest stable SDK, and run Hello World.
+
+```
+name: Dart
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+      - uses: dart-lang/setup-dart@v1
+
+      - name: Install dependencies
+        run: dart pub get
+
+      - name: Hello world
+        run: dart bin/hello_world.dart
+```
+
+## Check static analysis, formatting, and tests
+
+Various static checks:
+
+  1) Check static analysis with the Dart analyzer
+  2) Check code follows Dart ideomatic formatting
+  3) Check that unit tests pass
+
+```
+...
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Install dependencies
+        run: dart pub get
+
+      - name: Verify formatting
+        run: dart format --output=none --set-exit-if-changed .
+
+      - name: Analyze project source
+        run: dart analyze
+
+      - name: Run tests
+        run: dart test
+```
+
+## Matrix testing
+
+Double matrix across two dimensions:
+
+  - All three major operating systems: Linux, macOS, and Windows.
+  - Dart release channels: stable, beta, dev.
+
+```
+name: Dart
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  test:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+        channel: [stable, beta, dev]
+    steps:
+      - uses: actions/checkout@v2
+      - uses: dart-lang/setup-dart@v1
+        with:
+          channel: ${{ matrix.channel }}
+
+      - name: Install dependencies
+        run: dart pub get
+
+      - name: Run tests
+        run: dart test
+```
+
+# License
+
+See the [`LICENSE`](LICENSE) file.
\ No newline at end of file
diff --git a/action.yml b/action.yml
new file mode 100644
index 0000000..de24fa6
--- /dev/null
+++ b/action.yml
@@ -0,0 +1,12 @@
+name: "Setup Dart SDK"
+description: "Setup the Dart SDK, and add it to the PATH"
+inputs:
+  channel:
+    description: "The release channel to install from ('stable', 'beta', or 'dev')"
+    required: false
+    default: "stable"
+runs:
+  using: "composite"
+  steps:
+    - run: $GITHUB_ACTION_PATH/setup.sh ${{ inputs.channel }} ${{ runner.os }}
+      shell: bash
diff --git a/setup.sh b/setup.sh
new file mode 100755
index 0000000..da663cc
--- /dev/null
+++ b/setup.sh
@@ -0,0 +1,40 @@
+#!/bin/bash
+
+###############################################################################
+# Bash script that downloads and does setup for a Dart SDK.                   #
+# Takes three params; first listed is the default:                            #
+# $1: Dart channel: stable|beta|dev                                           #
+# $2: OS: Linux|Windows|macOS                                                 #
+# $3: ARCH: x64|ia32                                                          #
+###############################################################################
+
+
+# Parse args.
+CHANNEL="${1:-stable}"
+OS="${2:-Linux}"
+ARCH="${3:-x64}"
+OS=$(echo "$OS" | awk '{print tolower($0)}')
+echo "Installing Dart SDK from the ${CHANNEL} channel on ${OS}-${ARCH}"
+
+# Calculate download Url. Based on:
+# https://dart.dev/tools/sdk/archive#download-urls
+PREFIX="https://storage.googleapis.com/dart-archive/channels"
+URL="${PREFIX}/${CHANNEL}/release/latest/sdk/dartsdk-${OS}-${ARCH}-release.zip"
+echo "Downloading ${URL}..."
+
+# Download installation zip.
+curl --connect-timeout 15 --retry 5 "$URL" > "${HOME}/dartsdk.zip"
+unzip "${HOME}/dartsdk.zip" -d "${RUNNER_TOOL_CACHE}" > /dev/null
+if [ $? -ne 0 ]; then
+  echo -e "::error::Download failed! Please check passed arguments."
+  exit 1
+fi
+rm "${HOME}/dartsdk.zip"
+
+# Update paths.
+echo "${HOME}/.pub-cache/bin" >> $GITHUB_PATH
+echo "${RUNNER_TOOL_CACHE}/dart-sdk/bin" >> $GITHUB_PATH
+
+# Report success, and print version.
+echo -e "Succesfully installed Dart SDK:"
+${RUNNER_TOOL_CACHE}/dart-sdk/bin/dart --version