DDDD was designed with a Gamepad Controller in mind. MKB controls do work, but they're awkward. 

Start has dialogue. Endless is just gameplay.

CONTROLS

Left Stick, WASD - Move and aim shield.

Right Stick, Mouse - Move and aim cannon.

Right Trigger, Left Click, Spacebar - Shoot

Left Stick/D-pad, Arrow Keys - Navigate UI

Xbox A, Sony Cross, Nintendo B, Spacebar, Enter - Select

Xbox B, Sony Circle, Nintendo A, Spacebar - Skip Dialogue

Start, Esc - Pause or Exit