Use the arrow keys or WASD to move in the cardinal directions. Hold C (or K) plus a direction to place a colum using your Corpse Magic. This will cost you one vitality. Hold Z (or J) plus a direction to produce a bolt of magic. This costs two vitality, but saps one vitality from each monster it hits and gives it to you. You can destroy your own columns by attacking them but your magical bolts will not penetrate them.
Press the space bar or `.` to skip your turn.
A zap gives you one vitality for every monster you hit with it, so try to line up multiple monsters if you can.
Press Space to restart, once you've died.