It's a pretty basic game guru game. Game guru is a pretty crappy game creator, so you really have to put a lot into it to make a decent game.
One thing to note is how flat everything is. Once you go into the base everything is on one floor and it feels very flat. Another thing to add would be windows to make the base feel bigger then it is.
I would also add more ammo or a melee weapon. You're pretty much forced to just run around the monsters.