One game. Two worlds.
Classic chess… with a secret Underground!
Choose a Game Mode
SurfaceSurface layer
⇅Tunnel
UndergroundUnderground layer
HOW TO PLAY
Rules
Now you see it… now you don’t!
Switch to the matching square on the other layer—even to capture!
The knight’s secret shortcut
Knights jump in an L across layers to empty squares for free.
Every tunnel counts
Pawn count sets normal tunnels. Freeze stops two consecutive normal tunnels.
Out of tunnels? Not so fast!
Out of quota? Move your king onto the enemy king’s home square!
A check from another world
Watch out for a check from the matching square on the other layer!
The king’s escape route
The king has special check-escape tunnels—but not forever.
Where the kings meet
When escape chances run low, the layer where the kings meet becomes the final battleground — above or below.
How does it end?
Checkmate wins. Stalemate, repetition and draw rules can end the game.
Chess clock
Demo starts at 10 minutes per side. Every accepted human move earns +10 seconds; AI earns up to +10 seconds, capped at 84% of actual think time. Each game keeps its settings from when it started. You may pause and resume.