I'd love to hear some more details about the design decisions you made and any performance tradeoffs you ran into.
Otherwise, it's a great start. Some things you might consider:
* Better explosions. You can get pretty good effects with expanding/contracting colored circles, or using an animated sprite. I'm not sure what would be more efficient in html5. For an example check out the explosions in http://mochiland.com/articles/flash-game-friday-death-vs-mon...
* Reduce the size of the player's collision box. Most 'bullet hell' shooters actually use a box much smaller than the player sprite to give the player a bit of leeway as they try to dodge bullets.
* There's a pretty big size mismatch between the player and the enemies, maybe even that out a bit? The small enemies are cool because you can have a lot in a wave, but as a player the small enemies felt frustratingly hard to hit sometimes.
* Bullet image sprites. Guessing there's a performance issue here but I thought I'd suggest it anyways just in case you haven't tried it. A nice bullet sprite will make enemy bullets easier to read and easier for the player to dodge.
Otherwise, it's a great start. Some things you might consider:
* Better explosions. You can get pretty good effects with expanding/contracting colored circles, or using an animated sprite. I'm not sure what would be more efficient in html5. For an example check out the explosions in http://mochiland.com/articles/flash-game-friday-death-vs-mon...
* Reduce the size of the player's collision box. Most 'bullet hell' shooters actually use a box much smaller than the player sprite to give the player a bit of leeway as they try to dodge bullets.
* There's a pretty big size mismatch between the player and the enemies, maybe even that out a bit? The small enemies are cool because you can have a lot in a wave, but as a player the small enemies felt frustratingly hard to hit sometimes.
* Bullet image sprites. Guessing there's a performance issue here but I thought I'd suggest it anyways just in case you haven't tried it. A nice bullet sprite will make enemy bullets easier to read and easier for the player to dodge.