Quieter touch-sound after all

Moving charges really quickly was pretty loud when the sound got played
many times and overlayed.
Refactor angle and height info into game state

That way levels can define different level sizes.

The rendering doesn't support such an update yet though, as you'll see
if you enter the second level where heights increase by one.
Update sector-/height-lines on level change

Now levels can give what dimensions they want and have them render
properly.
Merge branch 'level-determined-mapsize'
Fix rendering in the case of only one orbit height

Now the single orbit height is just positioned at the average between
the minimum and maximum radii.
Some tutorial levels

Teaching one thing at a time.
Refactor level generation to expose level list
Little level indicators around planet

One per level
Light up level indicators as levels are completed
Level indicators on own layer

That way they aren't on top of the planet when animating in at the
start.
Merge branch 'level-indicators'
Add comments explaining level progression
Add stage teaching height-changing
Refactor level-changing to allow skipping levels

Skipping levels only at engine-abstraction though; not yet elsewhere but
calling `changeLevel` from console.
Bugfix: Creature shape on stage change

Creatures didn't check their `.direction` property on data update, so
they'd sometimes maintain the same path shape across level changes.