A trigger chain reaction in this puzzle is what happens when one chosen source unit on a populated 5-by-5 grid lights up and a deterministic wave spreads outward along discrete ticks, with every newly reached unit pulsing on the next step until the field is cleared or no new cell can be reached. You do not place pieces, connect neighbors, or spend turns building a path. The five original fields are already loaded with powered units, and the entire experiment runs from a single selection. Each unit has a visible power value from one to three that defines its Manhattan range, the number of horizontal plus vertical steps its outgoing wave can travel without diagonal shortcuts. The puzzle is therefore a test of reading positions and power together, choosing the source that can drive a chain across the whole field, and using the recorded tick groups to compare your forecast with what actually happened. Five full clears at 200 points each produce exactly 1,000 points.
The mental model is closer to a directed graph than a domino line. Each unit is a node with an outgoing radius; every other uncleared unit inside that radius is a candidate target for the next tick. Because cells are processed in a stable board-list order, the same trigger always produces the same tick groups, and because each unit activates only once, the wave cannot loop back on itself. The reaction does not describe a chemical, nuclear, biological, or electrical process. It is an abstract discrete graph game in which the word "reaction" simply labels a multi-step propagation rule.
What "Trigger Chain Reaction" Means in This Puzzle
Three formal rules define the trigger. First, the source you select emits on tick zero, and its power sets the maximum Manhattan distance any uncleared unit can receive from it on the next tick. Second, every unit that activates on a given tick forms one simultaneous frontier, and only that frontier emits during the following tick. Third, propagation ends when either every unit is cleared or the frontier of the previous tick had no uncleared cells inside its combined reach. The process is deterministic, so a wrong mental forecast always shows up as a tick group that stops before the field is empty.
Distance is the part most readers underestimate. A source with power two reaches any uncleared unit at distance two or less, but that distance is counted along horizontal and vertical steps only. A unit sitting two cells to the right is reachable; a unit sitting two cells diagonally is not, because the diagonal shortcut does not exist. Empty cells between the source and the target do not break the wave, unlike a domino chain where physical adjacency matters. The relevant questions are which units a candidate source can reach, which of those targets can in turn reach the rest of the field, and whether the resulting cascade covers every last cell.
How to Trigger a Chain Reaction Round
- Inspect every unit's grid position and visible power. Power is Manhattan range, so count horizontal plus vertical steps without diagonal shortcuts.
- Select one source unit by touch, click, or keyboard, then trigger the field. Newly reached units emit together on the next discrete tick.
- Study the recorded tick groups if the wave stops, choose a different source, and try again. Clear five fields at 200 points each for exactly 1,000.
The first step is the inspection. Before pressing any button, locate every unit on the grid and note its power number. Power one means a unit can reach up to four orthogonal neighbors, fewer from an edge or corner. Power three gives a wide radius that can cover much of the field in a single tick. The second step is target selection. Imagine the wave in frontiers: mark the source as tick zero, identify every target inside its range for tick one, and repeat from only those newly reached targets. Branching is valuable when separate regions of the field are covered by different tick groups. The third step runs the experiment and reads the result. The Tick recorder lists every observed wave as T0, T1, T2, and later steps, while cleared units shrink and display the tick on which they reacted. If the wave stops with uncleared units still on the board, the field can be reset and a different source tried. A field that clears every unit awards 200 points and unlocks the next experiment.
Reading Power and Position Together
High power alone is not enough to win a level. A unit with power three that sits in a corner with only weak neighbors in range can still leave most of the field untouched. The core question is which existing unit can start a directed cascade that eventually covers the whole field. Reading power and position together means asking three things at once: how many units can this source reach on tick one, can those tick-one targets reach the rest of the field on tick two and beyond, and does the combined frontier keep moving until no uncleared cell remains.
A useful relay is a unit whose own range adds new territory the source could not reach on its own. A remote low-power unit is often the hardest endpoint, so check which relay can reach it before committing to the trigger. Five original experiments progress from a short three-unit relay through longer fuses, a corner-to-corner handoff, a four-way bloom, and a final multi-branch surge. The grid size and rules never change. Difficulty grows through placement, power distribution, simultaneous waves, and directed reachability, not through new mechanics.
| Power value | Manhattan reach | Typical use |
|---|---|---|
| 1 | Up to 1 horizontal or vertical step | Reaches up to four orthogonal neighbors from a central position and short bridges |
| 2 | Up to 2 horizontal or vertical steps | Intermediate relays that span a small region in one tick |
| 3 | Up to 3 horizontal or vertical steps | Long-range hubs that anchor a frontier across a quadrant |
Tick Recorder and the Wave Front
The Tick recorder is the only feedback channel that matters for learning. After the trigger runs, the game lists every observed wave as T0, T1, T2, and later steps, and each cleared unit shrinks and shows the tick on which it reacted. The leaders of each group are the units that drove propagation on that step. A typical successful run on a five-unit field might show T0 with the source, T1 with the units on its range, T2 with everything those units could reach, and so on until the frontier empties.
Because the board is deterministic, you can compare a mental forecast with the exact recorded ticks and understand where an unsuccessful chain stopped. If the recorder shows T0, T1, T2, and then nothing, the only units that fired on tick two had no uncleared targets inside their combined range. The fix is to find a source whose tick-one frontier is closer to the regions of the field that were missed, so that the cascade geometry covers more territory earlier. Restarting a field is allowed, and the same field runs with the same rules every time, so two attempts with the same source produce identical tick groups.
Repairing a Failed Trigger
A trigger that leaves active units earns no points, but the run is not immediately over. Select a different source and run the field again. Repeating the identical failed trigger is deduplicated, so a double press does not consume another mistake. A second genuinely different failed source closes the run without a clear. When a corrected source succeeds after one failure, the failure record is cleared before the next level, so a single early slip on level one does not penalize the remaining four experiments.
This single-repair rule turns the puzzle into a planning exercise rather than a single-shot guess. The first attempt can chase the most ambitious cascade, and the second attempt can fall back to a safer but still complete source if the ambitious run stops early. Because the tick recorder is available before a successful clear, you can also use the first attempt as a probe: pick a likely source, watch where the wave stops, and use the recorded groups to pick a more central or higher-power source for the correcting run.
Controls for Triggering the Wave
Pointer and touch play use native unit buttons. Tap a unit to select it, then press Trigger selected unit. Keyboard play is scoped to the reaction field: focus a unit, use arrow keys to move through the available units, press Space to select, and press Enter to trigger. The Restart, Trigger, and Next experiment buttons retain their normal button behavior when they hold focus. Every unit control is at least 44 pixels high, the five-column field stays within a 390-pixel viewport, and status updates are announced with live text for screen reader users.
| Control | Pointer or touch | Keyboard |
|---|---|---|
| Move between units | Tap any unit on the 5x5 grid | Arrow keys cycle through available units |
| Select the source | Tap the desired unit | Press Space on the focused unit |
| Trigger the reaction | Press the Trigger selected unit button | Press Enter while the source is selected |
| Restart the field | Press the Restart button | Tab to Restart and press Space or Enter |
| Advance after a clear | Press the Next experiment button | Tab to Next experiment and press Space or Enter |
Everything runs locally in the browser. Source choices, tick records, mistakes, progress, and scores are not uploaded. No account, subscription, extra package, or server calculation is required. Independent tests verify every possible source for every field, lock each level's complete success set, prove every remaining choice stops early, and confirm exact scoring, deduplication, deadlock, restart equality, and spatial keyboard navigation. The Chain Reaction game stays open as a compact reasoning break, a visual introduction to directed reachability, and a way to practice separating simultaneous state changes into clear discrete steps.