1. Some squares can only be traversed once.
2. Wormholes. Not sure if I've seen this feature in a sokoban game before.
3. Landing on a solid white square (on the harder levels) causes new black cubes to appear.
There are over 50,000 players on the Leaderboard! Only 1 person has done all 90. A slew of people have done 89 levels. I've done about 50 levels.
Other Good Sokoban Puzzles
A Good Snowman is Hard to Build Charming
Go to Gold - superb
Go to Gold 2 - I hope a third version comes out.
Push Box Sokoban
Boxed In - loved this. First in a series of 4.
BoxWorld - awesome. I still remember struggling through levels 26 and 35 for days.
Paper & Light
Square Push Square
Test Chamber - brilliant
Duck Roll surprisingly very good
Color Labyrinth - excellent