work on it
I have never played halo.(but I want to)
here are my suggestions:
A work on more monsters.
B add a status bar.
C have the monsters attack instead of walk
across the screen.
D add different terrain styles. (ex: hallway
[front view], house, stairway[side view],etc.)
E start with a pistol, not a shotgun.
F move to differnt areas after a set time.
G add simple preloader game (tetris, tic tac
toe, space invaders,etc.) because all the
stuff I suggested will double the file size.
Things that you have going for ya:
1 breakable background, nice!
2 shotgun pic, cool as fudge!
I know what I am asking of ya is harsh but with work you might be on the top twenty.