QoL stuff, fixed holes, music

Smallish update, mostly bugfixes and a few improvements.

• Holes now work properly (or at least better than before)
• Hovering on a hole will show the falling spot
• Hovering on a numbered dude will show an overlay for all numbered dudes on the map
• You can now see when hidden blocks are active in gaps
• More sounds
• Music
• Improved snapping
• Things are more responsive to player input