Rings and Boxes

Rings and Boxes is a sokoban-style puzzle game about possession, replacement, swapping and switching. It is implemented indirectly by two weird objects, Rings and Boxes.

There are 50 levels +20 extra levels to test you.  Remember that you can skip any level. 

Rules:

• Put together rings and boxes of the same color.
• Except for black, colors have no special meaning.
• Your box can be exchanged.
• Extra boxes are OK.
• Rings and boxes of the same color stick together and stop.
• Rings and boxes of different colors can move together.

Controls:

• WASD/Arrow Keys to move
• Z to undo
• R to restart
• Esc for level select

Hackable source  is here.