Maxwell's puzzling demon v1.2.1

[h3]Levels update[/h3]

• The hint feature is now available in w3.
  
• Changed w3 and Added 3-17, 3-18, 3-19 and 3-H.
  
• Slightly changed 3-7.
  

[h3]Other changes[/h3]

• Fixed a bug that sometimes caused inconsistencies when undoing the turn you clear or reach levels.
  Note that this change now causes undo to rewind the progress if you undo the turn you clear or reach levels.
  
• After reaching 3-5, the history of the level transition are now displayed while holding shift.
  
• Implemented redo.
  
• Fixed a bug that camera doesn't work properly under a certain situation.