Use the lifetime limiters on Bullets & Asteroids

Closes #14

Despawn bullets to limit range.

Despawn asteroids to limit random garbage floating around the scene.

src/asteroids.rs

@@ -7,7 +7,7 @@ use std::time::Duration;
 
 use bevy::prelude::*;
 
-use crate::{GameAssets, WorldSize, physics::Velocity};
+use crate::{GameAssets, Lifetime, WorldSize, config::ASTEROID_LIFETIME, physics::Velocity};
 
 #[derive(Component, Deref, DerefMut)]
 pub struct Asteroid(AsteroidSize);
@@ -124,6 +124,7 @@ pub fn spawn_asteroid(
             Velocity(spawn.vel),
             Mesh2d(mesh),
             MeshMaterial2d(material),
+            Lifetime(Timer::from_seconds(ASTEROID_LIFETIME, TimerMode::Once)),
         ));
     }
 }

src/config.rs

@@ -17,5 +17,8 @@ pub(crate) const SHIP_THRUST: f32 = 1.0;
 pub(crate) const SHIP_ROTATION: f32 = 4.0; // +/- rotation speed in... radians per frame
 
 pub(crate) const BULLET_SPEED: f32 = 150.0;
+pub(crate) const BULLET_LIFETIME: f32 = 2.0;
+
+pub(crate) const ASTEROID_LIFETIME: f32 = 40.0;
 
 pub const RNG_SEED: [u8; 32] = *b"12345678909876543210123456789098";

src/lib.rs

@@ -8,9 +8,9 @@ mod title_screen;
 
 use crate::asteroids::{Asteroid, AsteroidSpawner};
 use crate::config::{
-    ASTEROID_SMALL_COLOR, BACKGROUND_COLOR, BULLET_COLOR, BULLET_SPEED, PLAYER_SHIP_COLOR,
-    SHIP_ROTATION, SHIP_THRUST, SHIP_THRUSTER_COLOR_ACTIVE, SHIP_THRUSTER_COLOR_INACTIVE,
-    WINDOW_SIZE,
+    ASTEROID_SMALL_COLOR, BACKGROUND_COLOR, BULLET_COLOR, BULLET_LIFETIME, BULLET_SPEED,
+    PLAYER_SHIP_COLOR, SHIP_ROTATION, SHIP_THRUST, SHIP_THRUSTER_COLOR_ACTIVE,
+    SHIP_THRUSTER_COLOR_INACTIVE, WINDOW_SIZE,
 };
 use crate::physics::AngularVelocity;
 use crate::ship::{Bullet, Ship};
@@ -340,6 +340,7 @@ fn input_ship_shoot(
             Mesh2d(game_assets.bullet().0),
             MeshMaterial2d(game_assets.bullet().1),
             ship_pos.clone(), // clone ship transform
+            Lifetime(Timer::from_seconds(BULLET_LIFETIME, TimerMode::Once)),
         ));
     }
 }