CacheSleuth

A slab slides back and forth above the top of the tower. Tap anywhere on the tower, or press the space bar or Enter, to drop it. Whatever overlaps the slab below survives, the overhang shears off, and the next slab enters at right angles.

Want one of these for your own cache?

Build it in a few minutes, no account needed, and you get a link to put on your cache page.

Build your own Cairn cache