Thank you for playing!
You can switch elements using the Q and E keys too. We initially designed the element nerf to be 0% damage, but playtesters found it too difficult to remember the "correct" elements under stress. So, we changed it to a 50% damage nerf and a 200% buff for using the correct element (with a 4x score bonus). The "punishment" is having a lower score and dodging more bullets for longer.
The bullet hitboxes are 2 pixels smaller than the sprites, though the lack of physics interpolation makes it hard to see when a hit is registered.
Rabbit and Steel inspired us to add the mouse-based movement!
The details are listed in the Game Manual/ Wiki. Hope this helps!