Cog Mahjong Solitaire
About the Cog Layout
The Cog layout is built as a mechanical gear seen face on: a thick circular ring of tiles forms the wheel, evenly spaced rectangular teeth jut outward all the way around the rim like the spokes of a sprocket, and a clean round hole sits empty at the very center. The teeth give the outer edge a satisfying scalloped silhouette, while the body of the ring is a continuous band of tiles that closes back on itself with no beginning and no end. It is one of the more architectural object boards, all hard angles and rotational symmetry, like a single part lifted straight out of a clockwork.
Rated 3 out of 5, the Cog sits squarely in the middle of the difficulty range and plays trickier than its tidy look suggests. The teeth around the rim are easy pickings, but the closed ring behind them can stack into short overlapping runs that hide tiles until their neighbors clear. Because the shape loops all the way around, there is no natural corner to unzip from, so you have to keep the whole wheel turning at once rather than working a single edge to exhaustion. It rewards players who like a board with a bit of bite.
Difficulty: Hard (3/5) | Tiles: 96
How to Clear the Cog Layout
Pull the teeth first. The rectangular tabs sticking out around the rim are almost all free on at least one side, so they are the easiest tiles on the board and the fastest way to thin things out. Knocking off the outer teeth also exposes the outer edge of the ring beneath them, opening up your next wave of moves around the whole circumference.
Once the teeth are gone, work the ring as a loop rather than a line. The wheel has both an outer rim and an inner rim facing the central hole, which means tiles in the band are often free on the inside or the outside. Alternate between attacking from the hole side and the rim side to peel the ring inward and outward at the same time, keeping moves available all the way around instead of cornering yourself on one arc.
The crux is the closed-loop geometry. With no open end, it is easy to clear three quarters of the ring and discover the final quarter has tiles boxed in on both sides by their own neighbors. Guard against this by removing tiles roughly evenly around the circle, so the ring thins like a shrinking band rather than getting eaten away from one spot. Keep an eye on matching pairs that sit on opposite sides of the wheel, and try to take them while both are still reachable.
For the endgame, the last tiles usually live in the body of the ring near where you started. Hold a flower or season tile back if you can, since it matches any flower or any season and can bridge an awkward gap in the band. If the loop locks up with unmatched survivors, use Shuffle to re-deal the remaining tiles solvably and reopen the wheel.
The Story Behind the Cog Layout
A cog, or gear, is one of humanity's oldest and most elegant machines, a wheel whose teeth bite into another wheel to pass motion and force along a chain of parts. The phrase a cog in the machine has come to mean a small but essential piece of something larger, which is a fittingly humble idea for a single gear floating on a Mahjong board. Its defining feature, those regularly spaced teeth, comes straight out of geometry, and that same strict spacing is exactly what makes it translate so cleanly into a grid of tiles.
The rotational symmetry is what makes the Cog fun to play. Most layouts have a clear up and down or a head and a tail, but the gear looks the same no matter how you turn it, which subtly changes how you read the board. You stop thinking in terms of left-to-right progress and start thinking in terms of keeping the whole wheel spinning evenly, a nice mental shift from the usual Mahjong flow.
Frequently Asked Questions
Where are the easiest tiles on the Cog board?
The teeth around the outer rim. Each tooth is a small tab that pokes out from the ring and is typically free on at least one side, making them the simplest tiles to remove. Clearing the teeth first also frees the outer edge of the ring for your next moves.
Why do I keep getting stuck on the last part of the ring?
Because the cog is a closed loop with no open end, so if you eat away one section too fast you can trap tiles that are blocked by their own neighbors on both sides. Remove tiles fairly evenly all the way around the circle to keep the band thinning as a whole rather than from a single arc.
Does the empty hole in the middle affect play?
Only helpfully. The central hole means the inner rim of the ring has open space beside it, so many ring tiles are free on their inside edge. Attacking from both the hole side and the outer rim is the key to peeling the wheel apart smoothly.
What makes the Cog a 3 out of 5 rather than easier?
The teeth are simple, but the looping ring behind them has short overlapping stacks and no corner to start from, so you must manage the whole circle at once. That extra planning bumps it to a moderate, middle-of-the-pack challenge.
See more Object Mahjong boards, or browse all layouts.
