A very simple implementation of Space Invaders using pure Javascript and Canvas.
This software is provided as-is without warrenty. Feel free to slice, dice, and otherwise transform the code as much as you like for your purposes (though as always, credit is appreciated).
Left/Right arrow - move the player's ship horizontally. Spacebar - player fires a projectile. r - reset the game enter - instawin (this was for debugging purposes)
Collision detection is crap. The code just checks to see if the projectile (treated as a point but drawn as a line) is within the boundingbox of a monster. This doesn't really affect gameplay much, and I'm not super interested in fixing things, but it's good to be aware of.
Have fun!
- Stephen