Great looking game and good, working gameplay. Music sounds good but perhaps the guitar could sound a little more chaotic to fit the atmosphere.
The enemies are fun to kill with the heavy feeling arm but some squishy sound of killing them with the arm would sound very fun. Also it felt quite uneven how many enemies, where and when they would come. After a big wave, there could come just one of them and it kills the multiplier streak. I would have preferred a standard wave system of enemies increasing overtime consistently. I would have liked for the pistol to have more impact too, it didn't feel very useful as it felt like you can just use the arm. Maybe the enemies could come faster to you at some point in the game so you need to knockback them more? I did very much like the chaotic feeling of the arm starting to lose total control!