Hard Mode

Keep moving at all times. Don't stand in the lava. Don't touch the kill balls.

Destroy all the generators to bring down the boss's shields. 

Controls

W, A, S, D to move. SPACE to jump. LEFT MOUSE to shoot. R to reload.

ESC at any time to pause and open the menu.

Strafe Jumping

Increase your max movement speed by strafe jumping. This will be required to survive at higher difficulties.