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Move magic numbers into constants in Breakout example (#4255)

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# Objective

- The Breakout example has a lot of configurable constant values for setup, but these are buried in the source code.
- Magic numbers scattered in the source code are hard to follow.
- Providing constants up front makes tweaking examples very approachable.

## Solution

- Move magic numbers into constants

## Context

Part of the changes made in #2094; split out for easier review.
This commit is contained in:
Alice Cecile 2022-03-19 23:05:02 +00:00
parent 738cd5e740
commit af24576b96
1 changed files with 77 additions and 47 deletions
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124
examples/game/breakout.rs
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@ -1,16 +1,53 @@
//! A simplified implementation of the classic game "Breakout"
use bevy::{ use bevy::{
core::FixedTimestep, core::FixedTimestep,
math::{const_vec2, const_vec3},
prelude::*, prelude::*,
sprite::collide_aabb::{collide, Collision}, sprite::collide_aabb::{collide, Collision},
}; };
/// An implementation of the classic game "Breakout" // Defines the amount of time that should elapse between each physics step.
const TIME_STEP: f32 = 1.0 / 60.0; const TIME_STEP: f32 = 1.0 / 60.0;
// These constants are defined in `Transform` units.
// Using the default 2D camera they correspond 1:1 with screen pixels.
// The `const_vec3!` macros are needed as functions that operate on floats cannot be constant in Rust.
const PADDLE_HEIGHT: f32 = -215.0;
const PADDLE_SIZE: Vec3 = const_vec3!([120.0, 30.0, 0.0]);
const PADDLE_SPEED: f32 = 500.0;
const PADDLE_BOUNDS: f32 = 380.0;
// We set the z-value of the ball to 1 so it renders on top in the case of overlapping sprites.
const BALL_STARTING_POSITION: Vec3 = const_vec3!([0.0, -50.0, 1.0]);
const BALL_SIZE: Vec3 = const_vec3!([30.0, 30.0, 0.0]);
const BALL_SPEED: f32 = 400.0;
const INITIAL_BALL_DIRECTION: Vec2 = const_vec2!([0.5, -0.5]);
const PLAY_AREA_BOUNDS: Vec2 = const_vec2!([900.0, 600.0]);
const WALL_THICKNESS: f32 = 10.0;
const BRICK_ROWS: u8 = 4;
const BRICK_COLUMNS: u8 = 5;
const BRICK_SPACING: f32 = 20.0;
const BRICK_SIZE: Vec3 = const_vec3!([150.0, 30.0, 1.0]);
const SCOREBOARD_FONT_SIZE: f32 = 40.0;
const SCOREBOARD_TEXT_PADDING: Val = Val::Px(5.0);
const BACKGROUND_COLOR: Color = Color::rgb(0.95, 0.95, 0.95);
const PADDLE_COLOR: Color = Color::rgb(0.5, 0.5, 1.0);
const BALL_COLOR: Color = Color::rgb(1.0, 0.5, 0.5);
const BRICK_COLOR: Color = Color::rgb(0.5, 0.5, 1.0);
const WALL_COLOR: Color = Color::DARK_GRAY;
const TEXT_COLOR: Color = Color::BLUE;
const SCORE_COLOR: Color = Color::RED;
fn main() { fn main() {
App::new() App::new()
.add_plugins(DefaultPlugins) .add_plugins(DefaultPlugins)
.insert_resource(Scoreboard { score: 0 }) .insert_resource(Scoreboard { score: 0 })
.insert_resource(ClearColor(Color::rgb(0.9, 0.9, 0.9))) .insert_resource(ClearColor(BACKGROUND_COLOR))
.add_startup_system(setup) .add_startup_system(setup)
.add_system_set( .add_system_set(
SystemSet::new() SystemSet::new()
@ -55,34 +92,37 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
commands commands
.spawn_bundle(SpriteBundle { .spawn_bundle(SpriteBundle {
transform: Transform { transform: Transform {
translation: Vec3::new(0.0, -215.0, 0.0), translation: Vec3::new(0.0, PADDLE_HEIGHT, 0.0),
scale: Vec3::new(120.0, 30.0, 0.0), scale: PADDLE_SIZE,
..default() ..default()
}, },
sprite: Sprite { sprite: Sprite {
color: Color::rgb(0.5, 0.5, 1.0), color: PADDLE_COLOR,
..default() ..default()
}, },
..default() ..default()
}) })
.insert(Paddle { speed: 500.0 }) .insert(Paddle {
speed: PADDLE_SPEED,
})
.insert(Collider::Paddle); .insert(Collider::Paddle);
// ball // ball
commands commands
.spawn_bundle(SpriteBundle { .spawn_bundle(SpriteBundle {
transform: Transform { transform: Transform {
scale: Vec3::new(30.0, 30.0, 0.0), scale: BALL_SIZE,
translation: Vec3::new(0.0, -50.0, 1.0), translation: BALL_STARTING_POSITION,
..default() ..default()
}, },
sprite: Sprite { sprite: Sprite {
color: Color::rgb(1.0, 0.5, 0.5), color: BALL_COLOR,
..default() ..default()
}, },
..default() ..default()
}) })
.insert(Ball { .insert(Ball {
velocity: 400.0 * Vec3::new(0.5, -0.5, 0.0).normalize(), // We can create a velocity by multiplying our speed by a normalized direction.
velocity: BALL_SPEED * INITIAL_BALL_DIRECTION.extend(0.0).normalize(),
}); });
// scoreboard // scoreboard
commands.spawn_bundle(TextBundle { commands.spawn_bundle(TextBundle {
@ -92,16 +132,16 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
value: "Score: ".to_string(), value: "Score: ".to_string(),
style: TextStyle { style: TextStyle {
font: asset_server.load("fonts/FiraSans-Bold.ttf"), font: asset_server.load("fonts/FiraSans-Bold.ttf"),
font_size: 40.0, font_size: SCOREBOARD_FONT_SIZE,
color: Color::rgb(0.5, 0.5, 1.0), color: TEXT_COLOR,
}, },
}, },
TextSection { TextSection {
value: "".to_string(), value: "".to_string(),
style: TextStyle { style: TextStyle {
font: asset_server.load("fonts/FiraMono-Medium.ttf"), font: asset_server.load("fonts/FiraMono-Medium.ttf"),
font_size: 40.0, font_size: SCOREBOARD_FONT_SIZE,
color: Color::rgb(1.0, 0.5, 0.5), color: SCORE_COLOR,
}, },
}, },
], ],
@ -110,8 +150,8 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
style: Style { style: Style {
position_type: PositionType::Absolute, position_type: PositionType::Absolute,
position: Rect { position: Rect {
top: Val::Px(5.0), top: SCOREBOARD_TEXT_PADDING,
left: Val::Px(5.0), left: SCOREBOARD_TEXT_PADDING,
..default() ..default()
}, },
..default() ..default()
@ -119,21 +159,16 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
..default() ..default()
}); });
// Add walls
let wall_color = Color::rgb(0.8, 0.8, 0.8);
let wall_thickness = 10.0;
let bounds = Vec2::new(900.0, 600.0);
// left // left
commands commands
.spawn_bundle(SpriteBundle { .spawn_bundle(SpriteBundle {
transform: Transform { transform: Transform {
translation: Vec3::new(-bounds.x / 2.0, 0.0, 0.0), translation: Vec3::new(-PLAY_AREA_BOUNDS.x / 2.0, 0.0, 0.0),
scale: Vec3::new(wall_thickness, bounds.y + wall_thickness, 1.0), scale: Vec3::new(WALL_THICKNESS, PLAY_AREA_BOUNDS.y + WALL_THICKNESS, 1.0),
..default() ..default()
}, },
sprite: Sprite { sprite: Sprite {
color: wall_color, color: WALL_COLOR,
..default() ..default()
}, },
..default() ..default()
@ -143,12 +178,12 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
commands commands
.spawn_bundle(SpriteBundle { .spawn_bundle(SpriteBundle {
transform: Transform { transform: Transform {
translation: Vec3::new(bounds.x / 2.0, 0.0, 0.0), translation: Vec3::new(PLAY_AREA_BOUNDS.x / 2.0, 0.0, 0.0),
scale: Vec3::new(wall_thickness, bounds.y + wall_thickness, 1.0), scale: Vec3::new(WALL_THICKNESS, PLAY_AREA_BOUNDS.y + WALL_THICKNESS, 1.0),
..default() ..default()
}, },
sprite: Sprite { sprite: Sprite {
color: wall_color, color: WALL_COLOR,
..default() ..default()
}, },
..default() ..default()
@ -158,12 +193,12 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
commands commands
.spawn_bundle(SpriteBundle { .spawn_bundle(SpriteBundle {
transform: Transform { transform: Transform {
translation: Vec3::new(0.0, -bounds.y / 2.0, 0.0), translation: Vec3::new(0.0, -PLAY_AREA_BOUNDS.y / 2.0, 0.0),
scale: Vec3::new(bounds.x + wall_thickness, wall_thickness, 1.0), scale: Vec3::new(PLAY_AREA_BOUNDS.x + WALL_THICKNESS, WALL_THICKNESS, 1.0),
..default() ..default()
}, },
sprite: Sprite { sprite: Sprite {
color: wall_color, color: WALL_COLOR,
..default() ..default()
}, },
..default() ..default()
@ -173,12 +208,12 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
commands commands
.spawn_bundle(SpriteBundle { .spawn_bundle(SpriteBundle {
transform: Transform { transform: Transform {
translation: Vec3::new(0.0, bounds.y / 2.0, 0.0), translation: Vec3::new(0.0, PLAY_AREA_BOUNDS.y / 2.0, 0.0),
scale: Vec3::new(bounds.x + wall_thickness, wall_thickness, 1.0), scale: Vec3::new(PLAY_AREA_BOUNDS.x + WALL_THICKNESS, WALL_THICKNESS, 1.0),
..default() ..default()
}, },
sprite: Sprite { sprite: Sprite {
color: wall_color, color: WALL_COLOR,
..default() ..default()
}, },
..default() ..default()
@ -186,19 +221,14 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
.insert(Collider::Solid); .insert(Collider::Solid);
// Add bricks // Add bricks
let brick_rows = 4; let bricks_width = BRICK_COLUMNS as f32 * (BRICK_SIZE.x + BRICK_SPACING) - BRICK_SPACING;
let brick_columns = 5;
let brick_spacing = 20.0;
let brick_size = Vec3::new(150.0, 30.0, 1.0);
let bricks_width = brick_columns as f32 * (brick_size.x + brick_spacing) - brick_spacing;
// center the bricks and move them up a bit // center the bricks and move them up a bit
let bricks_offset = Vec3::new(-(bricks_width - brick_size.x) / 2.0, 100.0, 0.0); let bricks_offset = Vec3::new(-(bricks_width - BRICK_SIZE.x) / 2.0, 100.0, 0.0);
let brick_color = Color::rgb(0.5, 0.5, 1.0); for row in 0..BRICK_ROWS {
for row in 0..brick_rows { let y_position = row as f32 * (BRICK_SIZE.y + BRICK_SPACING);
let y_position = row as f32 * (brick_size.y + brick_spacing); for column in 0..BRICK_COLUMNS {
for column in 0..brick_columns {
let brick_position = Vec3::new( let brick_position = Vec3::new(
column as f32 * (brick_size.x + brick_spacing), column as f32 * (BRICK_SIZE.x + BRICK_SPACING),
y_position, y_position,
0.0, 0.0,
) + bricks_offset; ) + bricks_offset;
@ -206,12 +236,12 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
commands commands
.spawn_bundle(SpriteBundle { .spawn_bundle(SpriteBundle {
sprite: Sprite { sprite: Sprite {
color: brick_color, color: BRICK_COLOR,
..default() ..default()
}, },
transform: Transform { transform: Transform {
translation: brick_position, translation: brick_position,
scale: brick_size, scale: BRICK_SIZE,
..default() ..default()
}, },
..default() ..default()
@ -239,7 +269,7 @@ fn paddle_movement_system(
// move the paddle horizontally // move the paddle horizontally
translation.x += direction * paddle.speed * TIME_STEP; translation.x += direction * paddle.speed * TIME_STEP;
// bound the paddle within the walls // bound the paddle within the walls
translation.x = translation.x.min(380.0).max(-380.0); translation.x = translation.x.min(PADDLE_BOUNDS).max(-PADDLE_BOUNDS);
} }
fn ball_movement_system(mut ball_query: Query<(&Ball, &mut Transform)>) { fn ball_movement_system(mut ball_query: Query<(&Ball, &mut Transform)>) {