Initial work on movement

src/main.rs

@@ -1,5 +1,14 @@
 use cat_box::{get_keyboard_state, Game, Sprite, SpriteCollection};
 use sdl2::keyboard::Scancode;
+use std::time::Duration;
+
+#[derive(Copy, Clone, Debug)]
+enum Direction {
+    Up,
+    Down,
+    Left,
+    Right,
+}
 
 fn main() {
     let game = Game::new("Snake", 1000, 1000);
@@ -11,15 +20,50 @@ fn main() {
         snake.push(s);
     }
 
+    let mut dir = Direction::Left;
+
     game.run(|ctx| {
         let keys = get_keyboard_state(ctx).keys;
 
         for key in keys {
-            if key == Scancode::Q {
-                game.terminate();
+            match key {
+                Scancode::Q => game.terminate(),
+                Scancode::W => dir = Direction::Up,
+                Scancode::A => dir = Direction::Left,
+                Scancode::S => dir = Direction::Down,
+                Scancode::D => dir = Direction::Right,
+                _ => (),
+            };
+        }
+
+        match dir {
+            Direction::Up => {
+                snake[0].translate((0, 37));
+            }
+            Direction::Left => {
+                snake[0].translate((-37, 0));
+            }
+            Direction::Down => {
+                snake[0].translate((0, -37));
+            }
+            Direction::Right => {
+                snake[0].translate((37, 0));
+            }
+        };
+
+        {
+            let mut last_part = snake[0].position();
+
+            for s in &mut *snake {
+                let (lastx, lasty) = last_part;
+                let (x, y) = s.position();
+                let (xdiff, ydiff) = (lastx - x, y - lasty);
+                s.translate((xdiff, ydiff));
+                last_part = s.position();
             }
         }
 
+        std::thread::sleep(Duration::from_millis(125));
         snake.draw(ctx).unwrap();
     })
     .unwrap();