Add keys to control volume
Add volume control instructions to main screen
"Enter" also selects titlescreen items
Add "space friction" to slow player down over time
Add a settings screen

This allows the player to set custom keybindings and modify the
space friction.
Leave a little empty time when level is complete

Leave some time between when all criteria for the level to be
complete are met and when the "Level complete" screen is shown.
This helps players know they have collected a powerup if it's the
last thing they're trying to do, and is a little less
disorienting in general.
Version 1.10