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Lizely

Tower Stack

Build a deterministic timing tower with exact overlap clipping, progressively narrower landings, keyboard control, and browser-verifiable pause-and-step alignment.

Privacy: your files never leave your device. All processing happens locally in your browser.

How to use

  1. 1.Watch the moving block, then click the playfield, choose Drop block, or press Space or Enter while it overlaps the tower top.
  2. 2.Expect every overhang to be clipped; pause with P and use Arrow keys or step buttons for deterministic one-unit alignment when desired.
  3. 3.Stack five successful blocks to score exactly 1,000; the first miss resets recoverably, while a second miss requires Restart.

About Tower Stack

Tower Stack is a deterministic timing and alignment game. A horizontal block moves back and forth above the current tower. Drop it while its span overlaps the top block. The overlapping interval becomes the next permanent level, while every overhanging part is clipped away. A centered landing preserves the current width. An offset landing makes the next level narrower, leaving less room for every later drop. A block with zero positive overlap misses the tower completely.

This Lizely edition uses a fully disclosed 100-unit track. The base occupies x 35 through x 65 and is 30 units wide. The first moving block also has width 30 but starts at x 0, so an immediate drop is a deterministic miss. Five successful blocks above the base complete the tower. The track size, base, speed progression, target, scoring, miss policy, and visual arrangement are original product rules rather than externally sourced physics, standards, or copied level data.

The pure logic layer is the source of truth. A moving block is represented by x position, width, direction, and speed. Every permanent block stores x, width, and level. Overlap is calculated as the larger left edge and smaller right edge of the moving and top spans. If the right edge is not greater than the left edge, the result is a miss. Otherwise the exact interval becomes the new block. No pixel sampling, canvas collision, CSS bounding box, animation frame time, or hidden answer decides the outcome.

Movement is also deterministic. Each tick advances by direction times speed. When the candidate x position crosses either track boundary, the pure transition reflects the excess distance back into the legal interval and reverses direction. The test runs 500 consecutive ticks and confirms that x never becomes negative and x plus width never exceeds 100. Speed increases after successful drops, raising the timing challenge while preserving the same tested reflection rule.

Click or tap the playfield, choose Drop block, or press Space or Enter to commit one atomic drop. Repeated keyboard events are ignored, so holding a key cannot create several blocks from one intended action. One call to the drop transition creates at most one permanent block and increments successful progress at most once. The moving block then resets at the left edge with the exact clipped width of the new top level.

Pause makes deterministic verification and accessible play possible without replacing the timing mechanic. Choose Pause or press P to stop automatic ticks. While paused, Step left, Step right, and the horizontal Arrow keys move the block exactly one unit per action within the same bounds. Resume restarts interval-driven motion. The timer performs no collision or score arithmetic; it only requests the next pure tick. This separation keeps browser animation behavior from becoming an untested second game engine.

A useful reproducible path pauses the game and places each moving block one unit to the right of the current top. The independent interval oracle then predicts widths 29, 28, 27, 26, and 25. The production transition produces exactly those same widths, with each new x equal to the overlap's left edge. After the fifth successful drop, the block list contains the base plus five levels and the score is exactly 1,000. Intermediate successful drops show 200, 400, 600, and 800 points.

The first complete miss records one mistake but is recoverable. The tower remains unchanged, and a fresh moving block with the current top width returns to x 0. The player can pause, realign, and continue building. A second miss records the second mistake and deadlocks the run until Restart. Because the initial moving block at x 0 and base at x 35 do not overlap, dropping immediately twice is a simple deterministic browser path for verifying the deadlock behavior.

Completion and deadlock are terminal states. Once either occurs, ticks, drops, pause toggles, and manual nudges return the unchanged state. Restart recreates the exact base, moving block, direction, speed, progress, score, pause state, and mistake count. The shared GameShell keeps only the best score in local browser storage and provides the double-Escape spreadsheet-style boss screen. Another double Escape returns to the same game state.

The release test independently calculates interval overlap instead of trusting the product overlap helper. It compares exact, one-unit overhang, partial, disjoint, and edge-touching spans. It proves that touching edges have width zero and count as a miss. It verifies the five-step narrowing path, score at every level, atomic block counts, first-miss recovery, second-miss deadlock, terminal freezing, pause stability, nudge bounds, and deterministic Restart.

The interface uses ordinary HTML buttons and positioned elements rather than a canvas library. Dynamic inline styles specify only geometric left, width, height, and bottom values; all colors, borders, typography, focus outlines, and surfaces come from site design tokens. The playfield, two-column mobile control grid, wrapping status text, and large actions fit a 390-pixel viewport without horizontal scrolling. Stable test identifiers expose stage, moving block, each permanent block, top geometry, direction, controls, feedback, completion, and deadlock.

Everything runs locally in the browser. No account, upload, random service, physics package, device sensor, audio, payment, server call, or new dependency is required. This fixed game is recreational rather than an intelligence, reflex, medical, educational, or employment assessment. Timing affects how easy alignment feels, but scoring depends only on reaching five valid drops. For a relaxed run, pause before each placement and nudge carefully; for a timing challenge, leave motion running and drop as the edges align.

Methodology & sources

Represent the track in 100 deterministic units. Reflect the moving span within zero through board width minus block width. On Drop, compute overlap start as max of left edges and overlap end as min of right edges; nonpositive width is a miss, while positive width becomes one new permanent level. Preserve the first miss as recoverable, deadlock on the second, score successful levels in 200-point steps, set exact score 1,000 on the fifth, and freeze terminal states. Independently verify interval arithmetic, 500 tick bounds, atomic transitions, the 30-to-25 narrowing path, recovery, deadlock, and Restart.

Frequently asked questions

How is the new block width calculated?
The game keeps only the positive horizontal overlap between the moving block and current top block. Any left or right overhang is clipped away.
Can I play without relying on reaction timing?
Yes. Pause the movement, then use Arrow keys or the step buttons to move exactly one unit at a time before dropping.
What happens when a block misses completely?
The first miss leaves the tower intact and resets a recoverable moving block. The second miss deadlocks the run until Restart.

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