Checklist of all the things

[mvasilkov]

• Check if we can do just one save-restore in _paintCurtain()
• Change State.buttonsPressed to bit mask
• Satisfying connection should change the color of the connected paint
• Make CanvasHandle(document.createElement('canvas'), ...) the default behavior if no canvas is provided
• Change functions that are passed as arguments to fat arrow syntax
• Add header comments to files
• Don't allocate new TileIntersection in ddaWalk
• Clean up console.log()
• Fold Hotspot._paintInternal() back into Hotspot.paintInternal() if not used
• Drop boundary checks in Level._fungusCol()
• Mangle properties using Terser
• Merge the 'Paint a tile' functions in Level.paintInternalTiles(), Level.paintInternalTiles2()
• Can use literal 10 and 20 instead of indices in LevelSelect._connect() to reduce size
• Can remove the baked crown from the princess' sprite to save bytes