Sudoku rules. Sequence chains. One addictive puzzle.

Dropoku is played on a 9×9 grid governed by standard Sudoku constraints — every row, column, and 3×3 box holds the digits 1–9 exactly once. Your job is to clear tiles by tracing chains, without ever leaving the board in an invalid state.

Tracing a chain

Tap a digit and drag through adjacent cells where each step is exactly +1 or −1 — for example 3→4→5→6. Release to clear the chain and score points. A chain needs a minimum of 3 tiles; anything shorter is rejected. Longer chains are worth exponentially more, so patience pays off.

Switch on Extended Mode from the mode-select screen and 1 and 9 wrap around, opening chains like 8→9→1→2.

Swapping tiles

Drag one tile onto an adjacent tile to swap their positions instead of chaining. If the swap opens up a valid chain, both tiles glow red — trace a chain through at least one of them to lock the move in. Changed your mind? Tap the Undo booster while the tiles are glowing to cancel the swap for free.

Gravity and cascades

After a chain clears, the tiles above fall to the lowest row that keeps the board Sudoku-legal — they'll never drop into a spot that would create a duplicate. Runs of 4 or more consecutive digits left on the board after a clear are auto-played as bonus cascades, so one good chain can set off several more.

Winning a level

Reach the target score before you run out of moves. Classic mode gives you a fixed move budget per level; Survival mode removes the move limit entirely and challenges you to keep chaining as long as possible.

Reading the HUD

The heads-up display above the board tracks your score, remaining moves, and a row of combo orbs that light up green, then amber, then red as your cascade streak grows — a quick glance tells you how hot your current run is. The chain preview at the bottom of the screen shows the exact sequence you're about to clear before you release, so you can bail out of a short chain and look for a longer one instead.

Chase length over speed

Because scoring is exponential with chain length, one 6-tile chain is worth far more than two 3-tile chains. Before you drag, scan the board for the longest run you can trace rather than clearing the first sequence you spot.

Engineer cascades on purpose

Use swaps to line up a run of 4 or more consecutive digits, then clear an adjacent chain and let gravity trigger the auto-cascade. Stacking cascades is the fastest way to light up every combo orb in the meter.

Bait a violation

If a swap leaves duplicate digits sitting side by side in a row or column, that entire row or column detonates for a large bonus. It looks like a mistake, but set up deliberately, it's one of the highest-scoring moves in the game.

Keep playing after the target

Hitting the target score earns your first star, but the level doesn't end there. Reach 1.4× the target for a second star and 2× for a third. Once you've earned all three stars, every remaining move automatically plants and detonates a bomb across a random 3×3 box — free bonus points on the way to the win screen.

Use special tiles deliberately

• Locked tiles can't join a chain and only clear once every neighbor around them is gone — plan your clears to isolate them early.
• Wild tiles connect to any digit, so save them to bridge chains that would otherwise be one tile short.
• Bomb tiles blast their entire 3×3 box when included in a chain — hold onto one until a box is packed with tiles you want gone.

Manage your boosters

Hint, Undo, and Shuffle are limited per level. Save Undo specifically for canceling a bad swap rather than mid-chain mistakes, since it's the only booster that can back out a committed move.

Try Rainbow Mode

Rainbow Mode replaces digits with colors along the spectrum (white → red → orange → yellow → green → blue → indigo → violet → black). All the same chaining and Sudoku rules apply — it's a great way to train chain recognition without relying on numbers.

Latest additions

The current build of Dropoku ships with the full combo system: cascading auto-chains, the 3-star target-and-beyond scoring curve, and the Bomb Finale that closes out a level once you've earned every star. Extended (wraparound) connection rules and Rainbow Mode tile styles are both available from the mode-select screen alongside Classic and Survival play.

What we're exploring next

We're actively looking at daily challenge boards with a fresh seed every 24 hours, a global leaderboard for Survival mode, and additional level packs beyond the current set. None of this is locked in yet — if you have a feature you'd want to see, let us know.