In each of 20 levels, you will have to reverse-engineer redstone circuits in order to figure out how to open the iron door at the end of the level.
The levels progress from easy to difficult and will test your redstone knowledge while exercising your logical thinking skills.
There are no hidden command blocks/structure blocks aside from those that operate the map (reset levels/teleport the player between levels, ect.)
NOTE: If you open the door, but it closes before you can get through to hit the button to take you to the next level, it doesn't count.