seen this
I have seen lots of flash that had almost exactly the same idea as this game...
a few tips to make this game a litle more fun:
1. As said by others before make more monsters
2. Give the monsters more special abilities like them shooting arrows back at
you that you can shoot out of the air.
3. Make the weapons you have react different here are a few ideas for effects:
Fire vould give a damage over time.
Bomb could be an area of effect weapon.
You can also make the weapons so that different monster can lose more
hitpoints to 1 kind of arrow while being more resistant to another.
4. Give the monsters types like fire which as i said above would than take more
damage from water or take less (or maybe be healed by) fire attacks.
5. Maybe you could make different characters whith different weapons for the
player.
6. When you hit a power up make a text appear that says what it does.
These where just a few ideas i hope you can use them.
For now im just going to give it a 5/10 3/5. keep trying.