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/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