expl-rel / snakegame_ocaml

The goal of this series of exercises is to teach you OCaml while implementing a game of snake.

Below is an an explanation of each exercise. The documentation here and embedded in the code will help guide you through each step along the way and also give you the tools to debug and understand the rest of provided code.

We encourage you to use your favorite editor to write the code; if you aren't already committed to one, we recommend using VSCode.

Exercise 00: Getting Started

=Compilation=

To compile your code while in this directory run

$ dune build

Each exercise has its own tests. To run the tests for exercise number N, run

$ dune runtest tests/exerciseN

To run the game of snake, run

$ dune exec bin/snake.exe

To kill the game, run Ctrl-C in the terminal you launched the game from.

As you can see, we've provided you with some framework code that creates the snake game and spawns an apple, but does nothing else. Not very exciting. Through the exercises that follow, you'll turn this into a fully working game!

NOTE: many of the exercises will have ignore statements at the top. The reason for this is OCaml complains about unused variables. The ignores are present so that you don't have issues running the game with parts not yet complete. When you start work on an exercise, you should remove all the ignores so that the compiler warns you about unused variables.

A few tips and hints:

• If you are seeing unexpected syntax errors in your editor (especially VSCode), try rebuilding the executable in the terminal.
• If you are trying to debug by running the snake game and the snake is moving too fast, a reasonable thing to do might be to temporarily decrease the speed of the snake. To do so, change the "0.1" to a larger value in the [handle_steps] function in run.ml.

Exercise 01: Moving Forward

Alright. The first thing we need to do is make it so the snake actually moves. In src/snake.ml, there is a function stub [move_forward], which is supposed to advance the snakes position one square. Open up that file, and read the exercise there.

Exercise 02: Turning

If you run the game now, the snake should walk forward until it reaches the edge of the black board, but it will never stop and will keep moving forever. There's also no way for you to interact with it, and there's nothing that ends the game. We'll tackle both of these, but let's work on making our game interactive by handling keyboard input first.

Let's complete:

• exercise 02a in src/direction.ml
• exercise 02b in src/game.ml

Exercise 03: Losing

As noted in the previous exercise, nothing currently prevents the snake from running off of the black game board. This is the next thing we're going to fix.

Let's complete:

• exercise 03a in src/board.ml
• exercise 03b in src/game.ml

Exercise 04: Self-collision

There's one more kind of collision that should end the game: the snake should die if it collides with itself. Once again there are two things we need to fix to make this happen.

Let's complete:

• exercise 04a in src/snake.ml
• exercise 04b in src/game.ml

Exercise 05: Spawning Apples

While playing with the game, you might have noticed that there is always a red dot that spawns on the board. This represents the apple that the snake is supposed to eat.

You may have noticed it always spawns in the exact same location. This is because in apple.ml, we hardcoded that location into the [possible_apple_locations] function, which is used to create the apple.

Let's fix this by completing exercise 05 in src/apple.ml

Exercise 06: Consuming Apples

Now our apple can spawn at an arbitrary location but it's still the case that nothing happens when the snake goes over the apple. We need to change it to consume the apple, and also cause the snake to grow over its next few steps.

Let's complete:

• exercise 06a in src/snake.ml
• exercise 06b in src/game.ml
• exercise 06c in src/snake.ml

Extensions

Amazing! We now have a minimally viable version of snake!

All exercises after this are extensions which will update and modify the game to make it more varied and more interesting. You can choose to implement any of these in any order, or come up with your own extensions.

Rather than intersperse the explanations amongst each file that you'll need to touch, each of these extensions is explained in full detail in Exercise##.mkd. The explanation will guide you to what files you need to modify, but you'll have to figure out the exact changes to be made by yourself.

If you would be excited to try some extensions that are not listed here, feel free to do those instead! Grab a TA if you want to talk about an extension that isn't listed here.

Exercise 07: Apple variants

There's no reason apples always have to be red. Exercise 07 will walk you through how to make different colors of apples that might have different behavior for the snake.

Exercise 08: Score

The win condition for the game is filling the board, but maybe displaying a current score would be nice. If you added different apple colors in exercise07 you could make them worth different amounts of points.

Exercise 09: Multiplayer

Competitive mode! This will show you how to add more snakes to the game so you can play against a friend.

Exercise 10: Restart game button

It'd be nice if we didn't have to kill and relaunch the game from the terminal every time we wanted to play again. In this exercise, you'll implement a button to restart the game.