Tap a gem colour in the forge row to see what it does, then press Forge. The gem goes into your pouch, or straight into a socket if you tapped an empty one first.
Drag a gem from your pouch onto a socket on the map. You can also tap the gem, then tap the socket.
Drag one gem onto another to merge. Two gems of the same grade make one gem a grade higher. Mixed gems keep most of each colour's power.
A gem's two strongest colours unlock a combo, such as Ruby + Emerald for Toxic Splash. Every pair of colours has one, listed below.
Grades stop at 10. Merge two grade 10 gems to make a Super gem. Pick one of two paths, then spend coins to raise it to level 3.
Each boss you beat lets you pick a relic, a perk for the rest of the run.
Traps are the diamond sockets on the path. Their hits are weak, but their powers are twice as strong.
Every 10th wave is a boss. Bosses drop shards even if you lose the run. Spend shards in the Forge.
Call the next wave early for bonus coins. Waves overlap, so do not get greedy.
Rage (button under the map) makes every coming wave tougher. Raging waves pay more coins, and each raging kill earns part of a shard.
You start with Ruby only. Spend shards in Gems to unlock more colours and to master the ones you have.
Handicaps open once you clear the first map. Each level makes runs harder and adds 15% to every shard you earn.