AWSZ to move. Space to Fire. You move left and right in jumps of 2 so be careful. You must shoot enough fuel dumps to continue your descent. Be careful not to press two keys at once. On the MC-10 (at least on the emulator) this can sometimes lock the keys from accepting input, until another key (from the two pressed together) is pressed. Try to keep keep presses discrete (sorry no joystick). 
