Separate tile drawing function.
Make the type of [Degree] and [Color] strict.
Debug unexpected behavior: you could not put the cursor but it is sticked to fixed tiles.
Color all tiles.
Inhibit division of [Pentagonal] number.
Convert division of [PentagonalRational] into multiplication of inverse of [PentagonalRational].
Make type of [Degree] strict.
Implement [Round].
Add stripe to all tiles.
Make flipping behavior more user-friendly.
Merge branch 'next'