Overall this is a good entry and I liked the visuals and the gameplay. It was however a bit hard to handle the enemies with just the arrows to find out where they're coming from. So, here are a few suggestions:
1. Make the ships smaller so that more of the map can be seen, or
2. Center the ship on the screen, or
3. Make a dynamic camera that focuses also on the incoming enemies
4. Have the enemies anounce themselves in a more pronouced way, like shooting and missing a couple of shots before actually targetting the player
5. Make bullets bigger... Much bigger...