Stack Tower

What is this game?

Stack Tower is a one-input timing game on an HTML5 canvas. A block slides horizontally above the tower; you drop it, and whatever part of it overlaps the block below becomes the new top. Everything that hung over the edge is lost, so each imprecise drop makes the next one harder.

The scoring hinges on one tolerance. If the dropped block's horizontal offset from the block below is four pixels or less, the engine treats it as perfect: it snaps the block into exact alignment, keeps its full width, and pays a combo bonus instead of a single point. Outside that window the block is trimmed to the overlap and your combo resets to zero.

Speed is not fixed. The block's travel speed is 240 pixels per second multiplied by the difficulty multiplier and then by a height term - 1 + min(height, 80) x 0.015 - so a tower climbs towards roughly twice the starting speed by the eightieth block, and then stops accelerating.

How to play

1. Pick a modeClassic runs until you miss badly enough to end it. Timed gives you a 60-second sprint to build as high as possible. Perfect Only is the hardcore variant: any drop outside the four-pixel window ends the run immediately.
2. Pick a difficultyThe difficulty is a speed multiplier on the sliding block: Casual 0.8x, Normal 1.0x, Fast 1.3x and Insane 1.65x. It changes how fast the block crosses the screen, not how wide the perfect window is - that stays at four pixels in every mode.
3. Drop the blockTap or click anywhere on the canvas, or press Space or Enter. There is no aiming step; the only decision is when.
4. Chase perfect drops, not just survivalA perfect drop keeps the block at full width and pays 2 + min(combo, 10) points, so a long clean streak is worth up to 12 points a block while a trimmed drop is worth 1. Combos are also the only way to stop the tower narrowing.
5. Read the game-over cardThe end screen gives your height, your score, your accuracy and whether you beat your stored best. Press R to restart straight away.

Controls

Click / Tap

Drop the sliding block - anywhere on the canvas works

Space / Enter

Drop the sliding block from the keyboard

P

Pause and resume the run

R

Restart, either mid-run or from the game-over card

Esc

Close the open modal, or pause and resume when no modal is open

Scoring and results

Height versus score

Height is how many blocks are standing. Score is what those blocks were worth: 1 point for a trimmed drop, or 2 + min(combo, 10) for a perfect one. Two players can reach the same height with very different scores, and the gap between them is entirely made of perfect drops.

PERFECT and the combo counter

A drop is perfect when the absolute difference between the new block's x position and the block below is at most four pixels. The engine then snaps x to match exactly, so a perfect run never loses a single pixel of width. The combo counts consecutive perfects and resets to zero on the first trimmed drop.

Accuracy

Accuracy is round(height / total drops x 100). Because a failed drop is still a drop, it reads as the share of your attempts that survived - not the share that were perfect.

Why the run ended

A run ends when the overlap is zero or less, or when the overlap is under 14 pixels and the drop was not perfect - the engine will not build on a sliver narrower than its minimum block width. In Perfect Only mode any non-perfect drop ends the run immediately and the reason is reported as MISSED PERFECT.

Stored bests

Best height, best score and the games you have played are kept per mode in localStorage under rtk_stack_tower_v1. Timed-mode results are tracked separately from Classic, so a 60-second sprint never overwrites an endurance record.

What this game tests

• Timing precision at a genuinely tight tolerance - four pixels, with the block starting at 396 pixels per second on Insane and accelerating from there
• Whether your precision holds as the block accelerates with tower height
• How long you can hold a perfect streak before the combo breaks
• Whether a 60-second limit changes how you play compared to an open-ended run
• How much of your score comes from precision rather than from surviving

Limits worth knowing

A browser can only report what the platform gives it. These are the honest boundaries of this page, so a result is never read as more than it is.

• The four-pixel window is measured in canvas pixels, not in physical millimetres. On a small phone screen the canvas is scaled down, so four canvas pixels cover less of your finger's travel - the tolerance is the same number but it feels tighter.
• Speed acceleration stops at height 80. The height term is 1 + min(height, 80) x 0.015, so a 200-block tower slides at exactly the same speed as an 80-block one. Long runs get harder because the tower has narrowed, not because it keeps speeding up.
• There is no undo and no continue. Once a drop trims the block the width is gone for the rest of the run, and the game-over condition is checked immediately rather than giving you a grace block.
• Records are per browser. Best height, best score and games played are written to localStorage under rtk_stack_tower_v1, so they do not travel to another device and clearing site data removes them.
• Audio is synthesised in the page with the Web Audio API and can be muted. No sound is required to play - the perfect window is judged visually and reported on screen.

Tips for a higher score

• Watch the block's edge, not its middle. Alignment is judged on the left edge's x position, so lining up the edges is exactly what the engine is measuring.
• Take the perfect streak seriously on Casual first. At 0.8x the four-pixel window is genuinely reachable, and a long combo is worth more than a tall sloppy tower - 12 points a block against 1.
• Use Timed mode to practise rhythm and Perfect Only to practise precision. Perfect Only punishes the exact mistake Classic lets you survive, which makes it the better trainer even though the runs are short.

Troubleshooting

Related documentation

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