109 lines
3.7 KiB
Rust
109 lines
3.7 KiB
Rust
//! A simplified implementation of the classic game "Breakout".
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use bevy::{
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prelude::*,
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};
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// These constants are defined in `Transform` units.
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// Using the default 2D camera they correspond 1:1 with screen pixels.
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const GAP_BETWEEN_PADDLE_AND_FLOOR: f32 = 60.0;
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const LEFT_WALL: f32 = -450.;
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const RIGHT_WALL: f32 = 450.;
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// y coordinates
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const BOTTOM_WALL: f32 = -300.;
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const TOP_WALL: f32 = 300.;
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const PARTICLE_SIZE: Vec2 = Vec2::new(10., 10.);
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// These values are exact
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const GAP_BETWEEN_PADDLE_AND_BRICKS: f32 = 270.0;
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const GAP_BETWEEN_BRICKS: f32 = 5.0;
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// These values are lower bounds, as the number of bricks is computed
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const GAP_BETWEEN_BRICKS_AND_CEILING: f32 = 20.0;
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const GAP_BETWEEN_BRICKS_AND_SIDES: f32 = 20.0;
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const BACKGROUND_COLOR: Color = Color::rgb(0.9, 0.9, 0.9);
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const BRICK_COLOR: Color = Color::rgb(0.5, 0.5, 1.0);
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fn main() {
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App::new()
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.add_plugins(DefaultPlugins)
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.insert_resource(ClearColor(BACKGROUND_COLOR))
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.add_startup_system(setup)
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.add_system(bevy::window::close_on_esc)
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.run();
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}
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#[derive(Component)]
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struct Brick;
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// Add the game's entities to our world
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fn setup(
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mut commands: Commands,
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) {
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// Camera
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commands.spawn(Camera2dBundle::default());
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// Paddle
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let paddle_y = BOTTOM_WALL + GAP_BETWEEN_PADDLE_AND_FLOOR;
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// Bricks
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// Negative scales result in flipped sprites / meshes,
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// which is definitely not what we want here
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assert!(PARTICLE_SIZE.x > 0.0);
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assert!(PARTICLE_SIZE.y > 0.0);
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let total_width_of_bricks = (RIGHT_WALL - LEFT_WALL) - 2. * GAP_BETWEEN_BRICKS_AND_SIDES;
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let bottom_edge_of_bricks = paddle_y + GAP_BETWEEN_PADDLE_AND_BRICKS;
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let total_height_of_bricks = TOP_WALL - bottom_edge_of_bricks - GAP_BETWEEN_BRICKS_AND_CEILING;
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assert!(total_width_of_bricks > 0.0);
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assert!(total_height_of_bricks > 0.0);
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// Given the space available, compute how many rows and columns of bricks we can fit
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let n_columns = (total_width_of_bricks / (PARTICLE_SIZE.x + GAP_BETWEEN_BRICKS)).floor() as usize;
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let n_rows = (total_height_of_bricks / (PARTICLE_SIZE.y + GAP_BETWEEN_BRICKS)).floor() as usize;
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let n_vertical_gaps = n_columns - 1;
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// Because we need to round the number of columns,
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// the space on the top and sides of the bricks only captures a lower bound, not an exact value
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let center_of_bricks = (LEFT_WALL + RIGHT_WALL) / 2.0;
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let left_edge_of_bricks = center_of_bricks
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// Space taken up by the bricks
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- (n_columns as f32 / 2.0 * PARTICLE_SIZE.x)
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// Space taken up by the gaps
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- n_vertical_gaps as f32 / 2.0 * GAP_BETWEEN_BRICKS;
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// In Bevy, the `translation` of an entity describes the center point,
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// not its bottom-left corner
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let offset_x = left_edge_of_bricks + PARTICLE_SIZE.x / 2.;
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let offset_y = bottom_edge_of_bricks + PARTICLE_SIZE.y / 2.;
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for row in 0..n_rows {
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for column in 0..n_columns {
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let brick_position = Vec2::new(
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offset_x + column as f32 * (PARTICLE_SIZE.x + GAP_BETWEEN_BRICKS),
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offset_y + row as f32 * (PARTICLE_SIZE.y + GAP_BETWEEN_BRICKS),
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);
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// brick
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commands.spawn((
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SpriteBundle {
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sprite: Sprite {
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color: BRICK_COLOR,
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..default()
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},
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transform: Transform {
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translation: brick_position.extend(0.0),
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scale: Vec3::new(PARTICLE_SIZE.x, PARTICLE_SIZE.y, 1.0),
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..default()
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},
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..default()
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},
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Brick,
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));
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}
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}
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}
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