Fix faster diagonal acceleration for the player

Also always accelerate the player using the same force, so that bigger players aren't overpowered.

src/game/objects.rs

@@ -6,9 +6,13 @@ use bevy::prelude::*;
 #[require(Collider, Mesh2d, MeshMaterial2d<ColorMaterial>, Restitution = Restitution::new(1.0), RigidBody, TransformInterpolation, Transform)]
 struct GameObject;
 
+/// Radius of a ball
+#[derive(Component, Default)]
+pub struct Radius(pub f32);
+
 /// A basic ball with which to interact
 #[derive(Component, Default)]
-#[require(GameObject, RigidBody = RigidBody::Dynamic)]
+#[require(GameObject, RigidBody = RigidBody::Dynamic, Radius)]
 pub struct Ball;
 
 /// The controllable ball

src/game/runtime.rs

@@ -1,3 +1,5 @@
+use core::f32;
+
 use avian2d::prelude::*;
 use bevy::{
     input::mouse::{AccumulatedMouseScroll, MouseScrollUnit},
@@ -5,32 +7,46 @@ use bevy::{
     prelude::*,
 };
 
-use super::objects::Player;
+use super::objects::{Player, Radius};
 
 /// Move the player character based on the keyboard input
 pub fn move_player(
     time: Res<Time>,
     keyboard_input: Res<ButtonInput<KeyCode>>,
-    mut velocity: Single<&mut LinearVelocity, With<Player>>,
-) -> Result {
-    let acceleration = 500.0;
+    mut query: Single<(&mut LinearVelocity, &Radius), With<Player>>,
+) {
+    let (ref mut velocity, radius) = *query;
 
-    let delta_v = acceleration * time.delta_secs();
+    let acceleration_energy = 150000.0;
+    // Although it would arguably be more accurate to divide by pi to get the actual mass (or include the density
+    // somehow), `acceleration_energy` is in arbitrary units so we can just pretend it's proper physics
+    let delta_v = acceleration_energy * time.delta_secs() / radius.0.powi(2);
+
+    let mut direction = Vec2::ZERO;
 
     if keyboard_input.any_pressed([KeyCode::KeyW, KeyCode::ArrowUp]) {
-        velocity.y += delta_v;
+        direction.y += 1.0;
     }
     if keyboard_input.any_pressed([KeyCode::KeyS, KeyCode::ArrowDown]) {
-        velocity.y -= delta_v;
+        direction.y -= 1.0;
     }
     if keyboard_input.any_pressed([KeyCode::KeyA, KeyCode::ArrowLeft]) {
-        velocity.x -= delta_v;
+        direction.x -= 1.0;
     }
     if keyboard_input.any_pressed([KeyCode::KeyD, KeyCode::ArrowRight]) {
-        velocity.x += delta_v;
+        direction.x += 1.0;
     }
 
-    Ok(())
+    // This would be easier if I could compare floats with 0 and still sleep at night
+    let circularize = if direction.x.abs() > 0.0 && direction.y.abs() > 0.0 {
+        f32::consts::FRAC_1_SQRT_2
+    } else {
+        1.0
+    };
+
+    // Kinda annoying I have to manually assign the fields here but I'll leave it in case I remember a better way later
+    velocity.x += direction.x * delta_v * circularize;
+    velocity.y += direction.y * delta_v * circularize;
 }
 
 /// Neatly exit game

src/game/setup.rs

@@ -12,7 +12,7 @@ use bevy_rand::prelude::{GlobalEntropy, WyRand};
 use rand::Rng as _;
 
 use super::{
-    objects::{Ball, Player, Wall},
+    objects::{Ball, Player, Radius, Wall},
     rng::thread_rng,
 };
 
@@ -32,6 +32,7 @@ pub fn setup_from_seed(mut commands: Commands, mut rng: GlobalEntropy<WyRand>) {
     ));
 }
 
+/// I mean, a camera is technically a user interface, I guess
 pub fn setup_ui(mut commands: Commands) {
     commands.spawn((Name::new("Camera"), Camera2d, IsDefaultUiCamera));
 }
@@ -44,10 +45,12 @@ pub fn setup_player(
 ) {
     let mut random = thread_rng();
 
-    let circle = Circle::new(random.random_range(BALL_SIZES));
+    let radius = random.random_range(BALL_SIZES);
+    let circle = Circle::new(radius);
     commands.spawn((
         Name::new("Player"),
         Player,
+        Radius(radius),
         Collider::from(circle),
         Mesh2d(meshes.add(circle)),
         MeshMaterial2d(materials.add(Color::from(LIME_400))),
@@ -64,18 +67,18 @@ pub fn setup_balls(
     let mut random = thread_rng();
 
     for i in 0..BALL_COUNT {
-        let circle = Circle::new(random.random_range(BALL_SIZES));
+        let radius = random.random_range(BALL_SIZES);
+        let circle = Circle::new(radius);
         commands.spawn((
             Name::new(format!("Ball[{i}]")),
             Ball,
+            Radius(radius),
             Collider::from(circle),
             Mesh2d(meshes.add(circle)),
             MeshMaterial2d(materials.add(Color::from(RED_400))),
             Transform::from_xyz(
-                random.random::<f32>() * (region.0 - 2.0 * circle.radius) + circle.radius
-                    - region.0 / 2.0,
-                random.random::<f32>() * (region.1 - 2.0 * circle.radius) + circle.radius
-                    - region.1 / 2.0,
+                random.random::<f32>() * (region.0 - 2.0 * radius) + radius - region.0 / 2.0,
+                random.random::<f32>() * (region.1 - 2.0 * radius) + radius - region.1 / 2.0,
                 0.0,
             ),
         ));