It won't work if you're just pressing buttons! Your mouse also has to be over the enemies! Not so easy now, is it?
Legions of enemies threaten you from every side! Your mouse and keyboard are your only weapons! MOUSE OVER an enemy, and press the key listed on them to kill them. They're all moving targets, and your nimble mouse has to be on top of them for it to work! Button-mash if you must, but pick your targets carefully.
Mouse over enemy and press key listed at same time. Green healthpacks and black bombs may appear when health is low, press both keys in a row to collect. Defend yourself as long as possible.