big update: new music! new level!

This is a real big update that adds a lot of functionality which could make this a completed game if you had extremely low standards.

There is now a main menu to switch levels--that's right, levels PLURAL! There are lives--lose all three and you get a game over screen. What's more, the levels, game over screen, and menu all neatly transition between each other. Who needs Starfield?

There's new original music on each of the levels, the title screen, and the game over screen. A robot sings to you about how you are dead and your game is over. (Click anywhere to go back to the main menu.)

There are real enemies--not just static targets! Enemy ships will now fly at you--if they hit you, you lose a life. Make sure to shoot them to keep safe and get that score up; maybe you'll win a prize (note: there are no prizes).

There are also some new graphical touches like a custom water shader on Level 1 and a starry night on Level 2.

As always, you can see my code on Github. Let me know if you're curious about something!