These are functions that are assigned to keys that, no matter what, you cannot change. As this might affect your Push-To-Talk functions, this can be handy to figure out what that key might be doing.

These are hardcoded even in the normal game. The mod did not add these, so this also applies to any Nuclear Throne runners out there that use Push-To-Talk.

Up: Up arrow

Down: Down arrow

Left: Left arrow

Right: Right arrow

Fire: Left mouse button

Active ability: Right mouse button

Swap weapons: Space, Mouse wheel up & down, Middle mouse button

Grab weapons: Shift, Control

Pause: P, F1, Escape

Select option: Enter

Back option: Escape

Y.V.'s horn: B

1 through 5: Select mutations

Thanks to /u/YellowAfterlife for finding all of these.