You must kill as many monsters as possible in this haunted house before you die. Killing monsters will earn you money which you can use to buy weapons an upgrades. The more monsters you kill, the harder the game will get.
Left and Right to move left and right.
Up to aim up.
Down to reload.
X to jump.
Z to pick up and throw items (including weapons).
C to shoot.
P to pause and enter the buy menu.