add 4th Yarwin suggestion:

"we are making use of delta (in line 79) therefore it should be delta instead of _delta 😅."

Author: FrankCasanova

squash-the-creeps/rust/src/player.rs

@@ -29,7 +29,7 @@ pub struct Player {
 }
 #[godot_api]
 impl ICharacterBody3D for Player {
-    fn physics_process(&mut self, _delta: f64) {
+    fn physics_process(&mut self, delta: f64) {
         let mut direction = Vector3::ZERO;
 
         let input = Input::singleton();
@@ -76,7 +76,7 @@ impl ICharacterBody3D for Player {
         // This is necessary for the is_on_floor() function to work as a body can always detect
         // the floor, walls, etc. when a collision happens the same frame.
         if !self.base().is_on_floor() {
-            self.target_velocity.y -= self.fall_acceleration * _delta as f32;
+            self.target_velocity.y -= self.fall_acceleration * delta as f32;
         }
         // moving the Character
         let velocity = self.target_velocity;