This game has good potential to be fun but it has some problematic flaws.
There is a bug with the music playing randomly many seconds after the game starting.
There is also no guide showing the controls for the game which would make it a problem for new players.
The EXP meter also does not function and would like to see it work in the future with it rewarding cool weapon upgrades and stuff.
Also there is no clear idea of what you are supposed to do in the game.
Also when you die ingame it does not reset or respawn and you are forced to reset the browser.
I understand this is just a demo but this information should help you make the game into a very good game, Hope to see your new improved version in the future.