Initial work on proper character movement

src/fighter/state/air.rs

@@ -0,0 +1,18 @@
+use bevy::prelude::*;
+
+use crate::fighter::{*};
+
+pub fn integrate_gravity(velocity: &mut FighterVelocity, attributes: &FighterAttributes) {
+    velocity.y -= attributes.gravity;
+    velocity.y = velocity.y.max(-attributes.terminal_velocity);
+}
+
+pub fn apply_air_motion(
+    velocity: &FighterVelocity,
+    translation: &mut FighterTranslation,
+    prev_translation: &mut FighterPreviousTranslation,
+) {
+    // Vertical velocity should be 0 on the ground
+    prev_translation.0 = translation.0;
+    translation.0 += velocity.0;
+}