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Bomb Defusal


Bomb Defusal

  {:jason, "~> 1.4"},
  {:kino, "~> 0.9", override: true},
  {:youtube, github: "brooklinjazz/youtube"},
  {:hidden_cell, github: "brooklinjazz/hidden_cell"}


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Ensure you type the ea keyboard shortcut to evaluate all Elixir cells before starting. Alternatively you can evaluate the Elixir cells as you read.

Bomb Defusal

We’re going to create a bomb defusal game.

There will be multiple bombs that need to be defused. If any of the bombs go off the entire game will be reset.

A BombSupervisor will supervise three Bombs. If any of the bombs detonate, every bomb detonates.


  S --> C1
  S --> C2
  S --> C3

That means when a Bomb process dies, the BombSupervisor will restart every Bomb process.

Create A New Mix Project

Using the command line, create a new supervised project in the projects folder called bomb_defusal.

mix new bomb_defusal --sup

Dialyzer, Credo, and ExDoc are optional for this project.

Create The Bomb GenServer

Create a Bomb GenServer. It should start as a minimal GenServer with no functionality.

Configure The BombSupervisor

Configure the BombSupervisor to start in application.ex. It should start with 3 Bomb GenServers as children.


Send a Bomb an :explode message. It should handle the message by terminating. The BombSupervisor should automatically restart all of the Bomb processes.

(Bonus) :cut

We will defuse bombs by sending them a :cut message with a :red, :white, or :black wire.

When a Bomb is initialized, it should store a randomized wire of either :red, :white, or :black in it’s state as the correct wire to defuse the bomb.

If the wire from the :cut message is correct, defuse the bomb.

A defused bomb will no longer terminal when sent the :explode message.

(Bonus) Timer

Add a Timer GenServer under the BombSupervisor tree.

The Timer should store a 5 minute timer which decrements every second.

Every time a :cut message is sent to a bomb with an incorrect value, the Timer should decrement by 30 seconds.

When the Timer reaches 0 it should terminate the BombSupervisor which should automatically restart under the application supervisor.

Mark As Completed

file_name = Path.basename(Regex.replace(~r/#.+/, __ENV__.file, ""), ".livemd")

progress_path = __DIR__ <> "/../progress.json"
existing_progress = File.read!(progress_path) |> Jason.decode!()

default = Map.get(existing_progress, file_name, false)

form =
      completed: input = Kino.Input.checkbox("Mark As Completed", default: default)
    report_changes: true

Task.async(fn ->
  for %{data: %{completed: completed}} <- Kino.Control.stream(form) do
    File.write!(progress_path, Jason.encode!(Map.put(existing_progress, file_name, completed)))


Commit Your Progress

Run the following in your command line from the curriculum folder to track and save your progress in a Git commit. Ensure that you do not already have undesired or unrelated changes by running git status or by checking the source control tab in Visual Studio Code.

$ git checkout solutions
$ git checkout -b bomb-defusal-exercise
$ git add .
$ git commit -m "finish bomb defusal exercise"
$ git push origin bomb-defusal-exercise

Create a pull request from your bomb-defusal-exercise branch to your solutions branch. Please do not create a pull request to the DockYard Academy repository as this will spam our PR tracker.

DockYard Academy Students Only:

Notify your instructor by including @BrooklinJazz in your PR description to get feedback. You (or your instructor) may merge your PR into your solutions branch after review.

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