Gradient on level-arranger
Make the level-arranger mouse boundary clearer
Display levelpack names in sidebar (abbreviated)
Render picked levels over top of UI
Don't error during level-arranging if you remove the start level
Change to levelpack when moving levels into it
Don't let LevelButton crash when it doesn't have a world
Refactor: remove levels from world while they're picked
Picked levels would render in the wrong place for a frame while being removed
Don't allow changing of start level from within editor