diff --git a/.editorconfig b/.editorconfig
new file mode 100644
index 0000000..8f0c87a
--- /dev/null
+++ b/.editorconfig
@@ -0,0 +1,7 @@
+[*.cr]
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+indent_style = space
+indent_size = 2
+trim_trailing_whitespace = true
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..23ec656
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,8 @@
+/doc/
+/lib/
+/bin/
+/.shards/
+
+# Libraries don't need dependency lock
+# Dependencies will be locked in application that uses them
+/shard.lock
diff --git a/.travis.yml b/.travis.yml
new file mode 100644
index 0000000..ffc7b6a
--- /dev/null
+++ b/.travis.yml
@@ -0,0 +1 @@
+language: crystal
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..d770aa8
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) 2018 Jon Egeland
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..82f83ee
--- /dev/null
+++ b/README.md
@@ -0,0 +1,48 @@
+# mtenv
+
+`mtenv` is a version manager for the Myst programming language, inspired by rbenv and other similar version managers.
+
+**It is currently a work in progress and should not be used for actual installations**. See the installation instructions in [Myst's README](https://github.com/myst-lang/myst#installation) for the time being.
+
+
+# Installation
+
+Since `mtenv` is contained in a single executable file, installing it is as simple as copying the single `mtenv` file to somewhere on your `$PATH`.
+
+From a command line, something as simple as
+
+```shell
+# Download the script
+curl -o mtenv 'https://raw.githubusercontent.com/myst-lang/mtenv/master/mtenv'
+# Copy it onto the `PATH`
+cp ./mtenv /usr/local/bin/mtenv
+# Make sure it's executable
+chmod +x /usr/local/bin/mtenv
+```
+
+And that's it! Running `mtenv` should now work and show you the usage instructions. However, `mtenv` also expects and depends on a `.mtenv` directory existing in your home directory (i.e., `~/.mtenv/`). This directory is used to store the installed versions of Myst and some other settings.
+
+When first installing `mtenv`, run `mtenv setup` to make sure this directory exists and has the proper content:
+
+```shell
+mtenv setup
+```
+
+`mtenv setup` will:
+
+  - ensure that `~/.mtenv/` exists and add some basic configuration.
+  - create `/usr/local/bin/myst` as a symlink to `~/.mtenv/shims/myst`, the executable that `mtenv` manages to control `myst` versions.
+
+Now you are fully set up to use `mtenv` and install new versions of Myst.
+
+_Note_: If you have existing versions of Myst installed via Homebrew or any other method, be sure to remove them from your PATH before using `mtenv`! Otherwise `mtenv` may not take precedence and may cause unexpected behavior._
+
+
+# Usage
+
+`mtenv` uses sub-commands to perform its various tasks. To see these commands listed out, just run `mtenv` to see the usage instructions. Further explanations are given here.
+
+- `mtenv install <version>`: install the version of Myst given by the argument. This will _not_ override the currently in-use version.
+- `mtenv version`: show the version number of the currently in-use version of Myst.
+- `mtenv installled`: show all currently-installed versions of Myst.
+- `mtenv available`: show all versinos of Myst that are available for installation.
diff --git a/shard.yml b/shard.yml
new file mode 100644
index 0000000..308f5e7
--- /dev/null
+++ b/shard.yml
@@ -0,0 +1,18 @@
+name: mtenv
+version: 0.1.0
+crystal: 0.24.1
+license: MIT
+
+description: |
+  The Myst language environment manager, inspired by rbenv and others.
+
+authors:
+  - Jon <jonegeland@gmail.com>
+
+targets:
+  mtenv:
+    main: src/mtenv.cr
+
+dependencies:
+  admiral:
+    github: jwaldrip/admiral.cr
diff --git a/spec/env_spec.cr b/spec/env_spec.cr
new file mode 100644
index 0000000..994e65d
--- /dev/null
+++ b/spec/env_spec.cr
@@ -0,0 +1,9 @@
+require "./spec_helper"
+
+describe Env do
+  # TODO: Write tests
+
+  it "works" do
+    false.should eq(true)
+  end
+end
diff --git a/spec/spec_helper.cr b/spec/spec_helper.cr
new file mode 100644
index 0000000..bd93df7
--- /dev/null
+++ b/spec/spec_helper.cr
@@ -0,0 +1,2 @@
+require "spec"
+require "../src/env"
diff --git a/src/commands/active.cr b/src/commands/active.cr
new file mode 100644
index 0000000..3a851d2
--- /dev/null
+++ b/src/commands/active.cr
@@ -0,0 +1,16 @@
+class MTENV
+  class Active < Admiral::Command
+    define_help description: "Show the currently-active Myst version."
+
+    def run
+      active_version = `cat #{File.expand_path("~/.mtenv/global")}`
+      if active_version.empty?
+        puts "No Myst version is currently active."
+      else
+        puts active_version
+      end
+    end
+  end
+
+  register_sub_command active : Active
+end
diff --git a/src/commands/available.cr b/src/commands/available.cr
new file mode 100644
index 0000000..e69de29
diff --git a/src/commands/implode.cr b/src/commands/implode.cr
new file mode 100644
index 0000000..0ed1b73
--- /dev/null
+++ b/src/commands/implode.cr
@@ -0,0 +1,35 @@
+class MTENV
+  class Implode < Admiral::Command
+    define_help description: "Completely uninstall mtenv and all Myst versions."
+
+    def run
+      require_confirmation!
+
+      unless Dir.exists?(File.expand_path("~/.mtenv"))
+        abort "~/.mtenv does not exist. Cannot ensure implosion."
+      end
+
+      shims_path = File.read(File.expand_path("~/.mtenv/shims_dir"))
+      puts ". Removing links to shims from #{shims_path}"
+      FileUtils.rm(File.join(shims_path, "myst"))
+
+      puts ". Removing `~/.mtenv`"
+      FileUtils.rm_r(File.expand_path("~/.mtenv"))
+
+      puts "Successfully imploded mtenv."
+    end
+
+
+    private def require_confirmation!
+      puts "Are you sure you want to completely uninstall mtenv? This cannot be undone."
+      puts "The `mtenv` command will remain installed, but all installations will be lost."
+      puts "Type 'implode' to confirm your intent."
+      print "> "
+      unless (confirmation = gets) && confirmation == "implode"
+        abort("Not uninstalling. Confirmation did not match 'implode'.")
+      end
+    end
+  end
+
+  register_sub_command implode : Implode
+end
diff --git a/src/commands/install.cr b/src/commands/install.cr
new file mode 100644
index 0000000..2612512
--- /dev/null
+++ b/src/commands/install.cr
@@ -0,0 +1,70 @@
+require "tempfile"
+
+class MTENV
+  class Install < Admiral::Command
+    define_help description: "Install a new version of Myst."
+
+    define_argument version : String,
+                    description: "A SemVer version number of commit SHA to install",
+                    required: true
+
+    define_argument name : String,
+                    description: "An alias name to use for the new installation."
+
+    GITHUB_URL = "api.github.com/repos/myst-lang/myst/tarball"
+
+    def run
+      Util.require_setup!
+      validate_version!
+
+      tarball = Tempfile.new("myst-#{version_name}", ".tar.gz")
+      if download_version_tarball(arguments.version, to: tarball.path)
+        install_location = File.expand_path("~/.mtenv/versions/#{version_name}")
+        FileUtils.mkdir_p(install_location)
+        unpack_tarball(tarball.path, to: install_location)
+        build_executable(install_location)
+      else
+        STDERR.puts "Could not find a Myst version matching '#{arguments.version}'."
+        exit(1)
+      end
+
+      tarball.unlink
+    end
+
+    def version_name
+      arguments.name || arguments.version
+    end
+
+
+    private def validate_version!
+      unless Util.versionish?(arguments.version)
+        STDERR.puts "'#{arguments.version}' is not a valid version identifier."
+        STDERR.puts "Versions must be given as either SemVer numbers (vX.X.X) or commit SHAs"
+        exit(1)
+      end
+    end
+
+    private def download_version_tarball(version, to file)
+      # curl GitHub for a tarball of the myst repository at the requested version.
+      # -sL     - run silently, and follow GitHub's redirects automatically
+      # > file  - output the content into `file`.
+      `curl -sL #{GITHUB_URL}/#{version} > #{file}`
+    end
+
+    private def unpack_tarball(tar_path, to destination)
+      # Unpack the given tar ball into the given destination.
+      # -xf                   - unpack from a file
+      # -C                    - sets the destination for the unpack
+      # --strip-components=1  - remove the containing directory name from GitHub.
+      `tar -xf #{tar_path} -C #{destination} --strip-components=1`
+    end
+
+    private def build_executable(install_location)
+      FileUtils.cd(install_location) do
+        `shards build`
+      end
+    end
+  end
+
+  register_sub_command install : Install
+end
diff --git a/src/commands/setup.cr b/src/commands/setup.cr
new file mode 100644
index 0000000..085a4d9
--- /dev/null
+++ b/src/commands/setup.cr
@@ -0,0 +1,59 @@
+require "file_utils"
+
+# The shim is written in `src/scripts/shim.sh`. This macro loads the content
+# of that file into a string at compile time, avoiding the need to use a
+# heredoc or bundle resource files when distributing this tool.
+MYST_SHIM = {{ "#{`cat #{__DIR__}/../scripts/shim.sh`}" }}
+
+class MTENV
+  class Setup < Admiral::Command
+    define_help description: "Ensure that `mtenv` is properly and fully installed."
+
+    def run
+      shims_location = ask_for_shims_location!
+      # Ensure the `.mtenv` dir exists in the home directory and has all of the
+      # necessary components (versions, global, shims, etc.).
+      FileUtils.cd(ENV["HOME"]) do
+        puts "Initializing `~/.mtenv/`"
+        FileUtils.mkdir_p(".mtenv/versions")
+        FileUtils.touch(".mtenv/global")
+        FileUtils.mkdir_p(".mtenv/shims")
+        # Store the shims location for use in the future (e.g., `implode`).
+        File.write(".mtenv/shims_dir", shims_location)
+
+        puts "Creating shims"
+        File.open(".mtenv/shims/myst", mode: "w", perm: 0o755) do |f|
+          f.truncate
+          f.puts(MYST_SHIM)
+        end
+
+        # Create mtenv-controlled shims for the Myst binary.
+        puts "Linking shims to #{shims_location}"
+        myst_path = File.join(shims_location, "myst")
+        File.symlink(File.expand_path("~/.mtenv/shims/myst"), myst_path)
+      end
+
+      puts "\nmtenv setup finished successfully."
+    end
+
+
+    private def ask_for_shims_location!
+      print "Where should mtenv create links to shims? (default '/usr/local/bin'): "
+      location = gets
+      if location.nil? || location.empty?
+        location = "/usr/local/bin"
+      end
+
+      location = File.expand_path(location)
+
+      if location && Dir.exists?(location)
+        return location
+      else
+        abort "Requested shims location `#{location}` does not exist. Aborting setup."
+      end
+
+    end
+  end
+
+  register_sub_command setup : Setup
+end
diff --git a/src/commands/uninstall.cr b/src/commands/uninstall.cr
new file mode 100644
index 0000000..bed22ec
--- /dev/null
+++ b/src/commands/uninstall.cr
@@ -0,0 +1,24 @@
+require "file_utils"
+
+class MTENV
+  class Uninstall < Admiral::Command
+    define_help description: "List all currently-installed Myst versions."
+
+    define_argument version : String,
+                    description: "The name of the version to uninstall",
+                    required: true
+
+    def run
+      version_path = File.expand_path("~/.mtenv/versions/#{arguments.version}")
+      if Dir.exists?(version_path)
+        puts "Uninstalling '#{arguments.version}'"
+        FileUtils.rm_r(version_path)
+        puts "Successfully uninstalled #{arguments.version}"
+      else
+        puts "Version '#{version_path}' is not an installed Myst version."
+      end
+    end
+  end
+
+  register_sub_command uninstall : Uninstall
+end
diff --git a/src/commands/use.cr b/src/commands/use.cr
new file mode 100644
index 0000000..869e3a7
--- /dev/null
+++ b/src/commands/use.cr
@@ -0,0 +1,26 @@
+class MTENV
+  class Use < Admiral::Command
+    define_help description: "Set the version of Myst to use."
+
+    define_argument version : String,
+                    description: "The name of the version to uninstall",
+                    required: true
+
+    def run
+      version_path = File.expand_path("~/.mtenv/versions/#{arguments.version}")
+
+      unless Dir.exists?(version_path)
+        abort "Version #{arguments.version} is not currently installed."
+      end
+
+      File.open(File.expand_path("~/.mtenv/global"), "w") do |f|
+        f.truncate
+        f.print(arguments.version)
+      end
+
+      puts "Active Myst version is now #{arguments.version}"
+    end
+  end
+
+  register_sub_command use : Use
+end
diff --git a/src/commands/versions.cr b/src/commands/versions.cr
new file mode 100644
index 0000000..08d4580
--- /dev/null
+++ b/src/commands/versions.cr
@@ -0,0 +1,11 @@
+class MTENV
+  class Versions < Admiral::Command
+    define_help description: "List all currently-installed Myst versions."
+
+    def run
+      Process.exec("ls", [File.expand_path("~/.mtenv/versions")])
+    end
+  end
+
+  register_sub_command versions : Versions
+end
diff --git a/src/mtenv.cr b/src/mtenv.cr
new file mode 100644
index 0000000..c75af2d
--- /dev/null
+++ b/src/mtenv.cr
@@ -0,0 +1,15 @@
+require "admiral"
+
+require "./util.cr"
+
+class MTENV < Admiral::Command
+  define_help description: "The Myst language environment manager."
+
+  def run
+    puts help
+  end
+end
+
+require "./commands/*"
+
+MTENV.run
diff --git a/src/scripts/shim.sh b/src/scripts/shim.sh
new file mode 100755
index 0000000..4309f90
--- /dev/null
+++ b/src/scripts/shim.sh
@@ -0,0 +1,11 @@
+current_version=`cat ~/.mtenv/global`
+
+if [ -z $current_version ]; then
+  echo "No version of Myst is currently active."
+  echo "Run \`mtenv use <version>\` to set a global version."
+  exit
+fi
+
+executable_path="~/.mtenv/versions/$current_version/bin/myst"
+
+`$executable_path $@`
diff --git a/src/util.cr b/src/util.cr
new file mode 100644
index 0000000..1539cc0
--- /dev/null
+++ b/src/util.cr
@@ -0,0 +1,41 @@
+module Util
+  extend self
+
+  # Determine whether the system is set up to run `mtenv`. If it is not, abort
+  # execution and inform the user of their installation problems.
+  def require_setup!
+    Dir.exists?(File.expand_path("~/.mtenv")) || fail_setup!("`~/.mtenv/` directory does not exist.")
+    Dir.exists?(File.expand_path("~/.mtenv/versions")) || fail_setup!("`~/.mtenv/installs` directory does not exist.")
+    File.exists?(File.expand_path("~/.mtenv/shims_dir")) || fail_setup!("`~/.mtenv/shims_dir` reference file does not exist.")
+  end
+
+
+  # Determine whether `version` is "versionish". That is, that it is able to
+  # indicate a specific version of Myst to install. This includes semver
+  # version numbers and commit SHAs, among potential others.
+  #
+  # The input is expected to already be trimmed.
+  #
+  # Returns true if `version` satisifies that condition, false otherwise.
+  def versionish?(version)
+    is_version = false
+    [
+      # SemVer release numbers:
+      #  v0.0.1
+      #  v1.0.2
+      #  v12.52.12
+      /^v\d+\.\d+\.\d+$/,
+      # commit SHAs (must be at least 7 characters long)
+      /^[0-9a-fA-F]{7,40}$/
+    ].any?{ |re| re.match(version) } || false
+  end
+
+
+  private def fail_setup!(message)
+    STDERR.puts("Setup check failed! Cause:")
+    STDERR.puts(message)
+    STDERR.puts("\n`mtenv` requires a valid setup to run.")
+    STDERR.puts("Run `mtenv setup` to attempt an automatic fix.")
+    exit(1)
+  end
+end