Space or click to shoot. The green bar is the amount of ammo you have. Once it reaches the bottom, press space or click to reload. The pink bar is how much health you have left. This is your health. It cannot be refilled. Use WASD to move.
I did not make the smooth movement script for the player, but I forget who did. (So feel free to comment about it). Also, if you beat the boss... good job. Nothing happens, though.