Escape the Crystal Mine goes down nine glittering levels, five chambers a level, along a zigzag of shafts. The new lock is Crystal Clusters. The bricks have grown together in clusters. A lone crystal shows its own number, but a bigger cluster shows only its weight, the total of its bricks. Every brick is the sum of the two below it.
A cluster is a sum you can use
A cluster weight is one equation about several bricks at once. Alone it is not enough, but combined with the pyramid rule it often pins everything down. Here is a made-up example.
One cluster, two lone crystals
The top is 30 and the bottom-right brick is 9, both lone crystals. The left brick of the middle row has grown together with the two bricks under it into one cluster of weight 26.
Spot the shortcut
The middle-left brick IS the sum of the two bricks under it. So the cluster is that brick counted twice: once as itself, once as its two parts. Twice that brick is 26, so the brick is 13.
The other middle brick
30 − 13 = 17.
Subtract down
The right middle brick is 17 and the bottom-right is 9, so the bottom middle is 17 − 9 = 8. Then the bottom-left is 13 − 8 = 5.
How hard can it get?
In the book the clusters get bigger and the shortcuts less obvious, and the early chambers use only the simplest moves. The Vault Lock at the end is a six-row board whose only facts are six gem weights, and every gem is needed.
How a page looks in the book
A low-resolution page from Escape the Crystal Mine, so you can see the layout. Nothing on it is solved.
Books mentioned
Escape the Crystal Mine
A puzzle adventure gamebook: go down nine glittering levels through 45 locked chambers, with 12 kinds of lock. Crystal Clusters is one of them.
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