043 : Collide with goal

We show the goal on the screen, but we want to detect when the player touches the goal and then end the game.

The first thing we need is a boolean variable that keeps track of whether or not the game is over. This should be initialized to false.

script.js: Add game_over variable.

function init_game() { ... // Game state. _game.game_over = false; _game.platform = create_platform(0, 360, _game.width, 40); _game.goal = create_goal(500, 360); // Global world parameters. ... }

Run your code in a browser and verify that there are no errors.

Now that we have this variable, we can set it to true when the player touches (collides with) the goal that we just added.

We do that by creating a new check_goal_collisions() function that checks for collisions between the player and the goal.

We're also temporarily adding a "dummy" version of the collide() function. This dummy version does nothing except return false (meaning no collision found). We'll be creating a proper version of collide() once we finish hooking up the goal collision code. We'll add a "NYI" comment to indicate that it's "Not Yet Implemented".

script.js: Create check_goal_collisions() function.

function check_platform_collisions() { ... } function check_goal_collisions() { var goal = _game.goal; if (collide(goal, _player)) { _game.game_over = true; } } // Return true if the 2 objects overlap. function collide(obj1, obj2) { // NYI return false; } // This is called ~60 times per second to update the world. function update_world() { ... }

Run your code in a browser and verify that there are no errors.

And finally, we can update check_collisions() to call this new function and check for goal collisions as well as platform collisions.

script.js: Call check_goal_collisions().

function check_collisions() { check_platform_collisions(); check_goal_collisions(); }

Run your code in a browser and verify that there are no errors.

The only thing missing is a proper implementation for the collide() function. We'll add that now.

GOTO 045