Player 1:

A/D for movement, W to jump, S to shoot, [space] to use special

Player 2:

Left/Right arrows for movement, Up arrow to jump, Down arrow to shoot, / to use special

Player 3:

G/J for movement, Y to jump, H to shoot, 5 to use special

Player 4:

{ / | for movement, = to jump, } to shoot, - to use special