From c02bf1c678380b0122ccb96090f69b00eb70ee09 Mon Sep 17 00:00:00 2001
From: Mike Hsu <mike.hsu@gmail.com>
Date: Mon, 15 Mar 2021 16:42:18 -0700
Subject: [PATCH] make physics systems dependent on TIME_STEP

---
 examples/game/breakout.rs | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/examples/game/breakout.rs b/examples/game/breakout.rs
index 444baf7595834..9cfdfb8448136 100644
--- a/examples/game/breakout.rs
+++ b/examples/game/breakout.rs
@@ -6,6 +6,7 @@ use bevy::{
 };
 
 /// An implementation of the classic game "Breakout"
+const TIME_STEP: f32 = 1.0 / 60.0;
 fn main() {
     App::build()
         .add_plugins(DefaultPlugins)
@@ -15,7 +16,7 @@ fn main() {
         .add_stage(
             FixedUpdateStage,
             SystemStage::parallel()
-                .with_run_criteria(FixedTimestep::step(1.0 / 60.0))
+                .with_run_criteria(FixedTimestep::step(TIME_STEP as f64))
                 .with_system(paddle_movement_system.system())
                 .with_system(ball_collision_system.system())
                 .with_system(ball_movement_system.system()),
@@ -62,7 +63,7 @@ fn setup(
             sprite: Sprite::new(Vec2::new(120.0, 30.0)),
             ..Default::default()
         })
-        .with(Paddle { speed: 8.0 })
+        .with(Paddle { speed: 500.0 })
         .with(Collider::Paddle)
         // ball
         .spawn(SpriteBundle {
@@ -72,7 +73,7 @@ fn setup(
             ..Default::default()
         })
         .with(Ball {
-            velocity: 6.0 * Vec3::new(0.5, -0.5, 0.0).normalize(),
+            velocity: 400.0 * Vec3::new(0.5, -0.5, 0.0).normalize(),
         })
         // scoreboard
         .spawn(TextBundle {
@@ -194,7 +195,7 @@ fn paddle_movement_system(
 
         let translation = &mut transform.translation;
         // move the paddle horizontally
-        translation.x += direction * paddle.speed;
+        translation.x += direction * paddle.speed * TIME_STEP;
         // bound the paddle within the walls
         translation.x = translation.x.min(380.0).max(-380.0);
     }
@@ -202,7 +203,7 @@ fn paddle_movement_system(
 
 fn ball_movement_system(mut ball_query: Query<(&Ball, &mut Transform)>) {
     if let Ok((ball, mut transform)) = ball_query.single_mut() {
-        transform.translation += ball.velocity;
+        transform.translation += ball.velocity * TIME_STEP;
     }
 }