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