2. The grid is white. Black squares will sometime have to be filled. If a square is marked with a green +, that means that if a green square is pushed onto it, it will be locked in place.
There's a lot more to say about this game, but I'll let you see for yourself. It's got everything: 'aha' moments, lots of levels etc. I have not solved all the levels.
I'm not crazy about the graphics. But that's okay. The content is what's important. New elements are presented with easy levels and then things get gradually harder.
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
Leonard Cohen died yesterday. My favorite version of his song Sisters of Mercy: https://www.youtube.com/watch?v=uNlfvO_1V5w