The controls are broken
It is a good concept but the graphics aren't that great & the controls are a bit clunky.
Programming is fine, but very poor game design. Needs something along the line of levels and/or upgrades. Also, the controls are a bit unresponsive and the timer for the vanishing pick ups is too short.
Fix the background so it doesn't move with you, make the AI in the monsters a little smarter, and fix the keypresses so that moving is easier (get rid of the elses in front of your if statements).