Running FlappyCollision/flappy_dragon_base:

error[E0425]: cannot find value `impulse` in this scope
   --> FlappyCollision/flappy_dragon_base/src/main.rs:205:7
    |
205 |       impulse.send(Impulse {
    |       ^^^^^^^ not found in this scope

It’s missing from the function signature. Also, for some reason, the impulse being applied is zero, so flapping doesn’t work even after fixing the compilation error:

      impulse.send(Impulse {
        target: flappy,
        amount: Vec3::ZERO,
        absolute: false,
      });

Anyway, easy fixes for these. I’m really enjoying working through the book! Looking forward to more!