🏗️ Stack It

What actually happens on every drop

Your tower starts on a base slab exactly 140 pixels wide. Each new block slides in from off-screen, picking left or right at random, and it is always the same width as the block it will land on. It keeps bouncing between the walls until you tap the game area or press Space. There is no auto-drop and no timer, so you can watch as many passes as you like before committing.

When you drop, the game measures how much of the new block sits over the one below. Anything hanging off the edge is sliced away for good, and the block that stays is only as wide as the overlap. That narrower block becomes the target for the next one. The tower can only ever shrink inward; it never grows back out past the base.

Two thresholds decide everything. If you are off by less than 5 pixels, it counts as a Perfect: the block snaps into exact alignment and keeps its full width. If 4 pixels or less overlap, the block misses, the tower topples, and the run is over. Anything in between is an ordinary drop that costs you width.

Scoring, with a worked run

The Height counter is really your score. An ordinary drop adds 1. A Perfect adds 2, because you get the block plus a 1-point bonus, and the status line flashes PERFECT! +1 bonus. So a Height of 30 might be 30 blocks, or 20 blocks with 10 Perfects.

Here’s a sample opening. Drop one lands 12 pixels off: width falls from 140 to 128, Height 1. Drop two is 3 pixels off, a Perfect: width stays 128, Height 3. Drop three is 20 pixels off: width 108, Height 4. Three blocks in, you have already spent 32 of your 140 pixels, and the Perfect was the only drop that cost nothing.

Your best Height is saved in this browser and shown next to the live counter. The ↻ button in the top bar wipes the current run and starts fresh at once, which is handy when the first two drops go badly.

The speed curve and the width budget

The block starts at 2.2 pixels per animation frame and speeds up by 0.12 for every point you score, up to a cap of 6. That cap kicks in at a Height of 32. On a standard 60Hz screen that is about 130 pixels per second at the start and 360 at full speed, which squeezes the Perfect window from roughly 75 milliseconds down to under 30.

Here’s the twist: because a Perfect is worth 2 points, it also speeds the block up twice as much. A Perfect-heavy run hits top speed after fewer blocks than a sloppy one. That is fine, because width is the resource that actually ends runs.

Think of the 140 pixels as a budget. Every ordinary drop spends exactly as many pixels as you were off by. If your misses average 8 pixels, you can afford about 16 of them before the tower is a sliver. Perfects are free. Getting past 50 means stacking long chains of Perfects, not taking a lot of near misses.

Beginner mistakes that end runs early

The block is at its slowest early on, so a short run usually comes down to habit, not speed. Watch for these.

• Tapping on the first pass. The block appears off-screen and races across. Let it bounce once so you can see its rhythm before you drop.
• Watching the moving block instead of the edges. Line up its leading edge with the edge of the stack below; that one alignment decides the cut.
• Panicking after a big slice. A narrow tower is not a dead tower. Width only matters while it can absorb error. At any width, a Perfect still keeps you alive.
• Tapping off the game area. Drops register on the game area itself or with Space. On a laptop, Space is steadier than a mouse click.

Intermediate and advanced technique

Pick one reference edge and use it every time. Many players lock their eyes on the left edge of the top block and drop the moment the moving block’s left edge reaches it, whichever way it is sliding. If you use the same cue every time, your timing becomes muscle memory instead of a guess.

Train both directions. Each block picks its starting side at random, so you will get runs of left-to-right blocks and then a sudden right-to-left one. Most players lean early one way and late the other. Watch which direction your ordinary drops come from and correct for that side.

Past Height 32 the speed stops rising, so nothing gets harder from there except your nerves. Many players find the high 30s steadier than the high 20s, where the speed was still changing.

A quirk of the thresholds helps with very thin towers. Once the top block is under about 10 pixels wide, a block either lands as a Perfect or misses, because there’s no room left for an ordinary cut. Every surviving drop at that width is worth 2 points, so a sliver tower that hangs on scores fast.

Where the stacking game comes from

Timing-stack games go back to arcade prize machines like LAI Games’ Stacker, where rows of lit squares slide across and any square that misses the row below drops off. The mobile hit Stack from Ketchapp turned the idea into the endless, sliced-block format most people know today. Stack It follows that one-button design: a single input, a single shrinking resource, and no luck once the block is moving.

Stack It FAQ