improve checks for RANDOM20:
- not more than 5 narrow 1 brick gaps (vert or hori)
- allow max 50% bricks on lowest 2 lines

polish editor:
- support for 4:3 classic layout (bricks/extras not shown right now)
- properly translate ids to chars to init test level
- preview of levels
- undo/redo stacks with snapshot before/after each action
- translation

menu for gamepad
warp mouse for absolute position to keep inside playing field

new extras
- free paddle y movement
- move level down 1
- instant death
- instant warp
- smaller/bigger balls (?)
- laser (clears entire row, limited number of shots)
- net: permanent, bring back one lost ball
- compatibility with old themes: choose random bonus/malus
  if not supported or write name in box

