You can repair a single failed trigger in Chain Reaction, and the game is built around that exact decision: pick one source unit, watch a deterministic wave spread to nearby powered units on discrete ticks, and adjust your choice if the first source leaves any unit uncleared. Chain Reaction is a five-level trigger puzzle played on a fixed five-by-five grid where every unit shows a power value from one to three and emits its wave in horizontal plus vertical Manhattan steps. When a selected source fails to clear the field, the run is not yet over; one replacement source can be tried, and repeating the identical failed source does not consume a second mistake. Five fields cleared at 200 points each produce the exact maximum score of 1,000, and one repaired mistake does not carry over to the next experiment. The repair mechanic is what turns the puzzle into a reading exercise instead of a guessing exercise, because the field is already populated and one selection launches the entire experiment from the start.
This repair mechanic exists because the puzzle is about reading the board before committing, not about reacting to a partial cascade. The field is already populated and one selection launches the entire experiment, so a wrong first guess is a normal part of solving rather than an error that punishes you out of the run. Understanding the failure rules and the recorded tick data is the difference between restarting the level and finishing it on the first cleared attempt.
What Counts as a Failed Trigger
A trigger fails when the chosen source emits on tick zero, the wave propagates outward through any uncleared unit inside its Manhattan range on each subsequent tick, and the process ends before every unit is cleared. The source itself counts as cleared, and any unit reached within range activates on the next tick, but if no remaining unit can be reached from the active frontier, the cascade stops early. Every triggered source is deterministic, so the same starting unit always produces the same tick groups and the same final state. A trigger that leaves active units earns no points for that field, and the game then offers a single repair attempt before the run closes.
The Tick recorder lists every observed wave as T0, T1, T2, and later steps. Cleared units shrink and display the tick on which they reacted, so after a failed run you can read exactly which frontier stopped and which unit was left untouched. That visible data is computed result data rather than decoration, and it is the most useful guide for choosing a replacement source on the same board.
Repairing a Failed Trigger in Chain Reaction
The repair flow is short and visible. After a failed trigger, the field stays on screen with its remaining uncleared units, and a second source can be selected without resetting the level. Use the steps below to convert a failed run into a 200-point clear.
- Leave the failed field on screen and read the Tick recorder. Identify the last tick that produced new activations and the unit that was left uncleared when the wave stopped.
- Locate an untouched unit whose Manhattan range can reach the leftover cell directly. Remember that range is horizontal plus vertical steps with no diagonal shortcut, and empty cells can be crossed.
- Tap that unit, or focus it with arrow keys and press Space, so it becomes the new selection. Confirm that no other unit on the board reaches further or covers more separate regions from its position.
- Press the trigger control for the new source. Watch the next discrete tick light up the units inside its range, and follow the simultaneous frontiers as the cascade expands.
- If the new source clears the field, the level awards 200 points and the failure record for that field is reset before the next experiment loads. If the new source also fails, the run closes and the field awards no points.
For the underlying controls and tick notation, the Chain Reaction game exposes pointer, touch, and keyboard play through the same unit buttons, and every unit control is at least 44 pixels high so the repair selection stays accessible.
Reading the Tick Groups After a Failed Trigger
The Tick recorder is your repair map. Each label such as T0, T1, T2, or T3 marks the units that lit up together on that discrete step. When the wave stops, the label simply stops appearing: the last group written down is the last frontier that emitted, and everything still uncleared is what the next source has to reach.
| What you see in the recorder | What it means for repair |
|---|---|
| Tick groups stop at T1 and one corner is uncleared | The original source only reached a single neighbour. Pick a source whose range spans the empty corner directly. |
| Tick groups stop at T2 with two distant units uncleared | Your source had no relay that could carry the wave to those cells. Find a unit inside their shared reach. |
| Tick groups stop at T3 and a single low-power unit is left | The wave almost completed. Look for any uncleared unit whose Manhattan range covers that leftover cell and trigger from there. |
| Tick groups reach every unit by T4 and the field is cleared | Successful run. 200 points awarded and the failure record resets for the next experiment. |
The exact tick numbers vary by field, but the diagnosis is always the same. The frontier that stopped tells you the region no chosen unit could bridge, and the unfilled cells tell you where the replacement source needs to aim.
Manhattan Distance: The Reach Rule Behind the Wave
Range in Chain Reaction is Manhattan distance, which means the count of horizontal steps plus vertical steps between two cells, with no diagonal shortcut. If a source sits at column two, row one with power two, it can reach any uncleared unit whose coordinates differ by a total of two or fewer steps in combined row and column movement. For example, a source at (2, 1) reaches (2, 3) because the column delta is zero and the row delta is two, giving a Manhattan distance of zero plus two, equal to two. The same source does not reach (4, 4), because the column delta is two and the row delta is three, giving a combined distance of five, which sits outside its power of two.
This rule is what makes source selection a planning problem. A high-power unit that sits in the wrong place can still leave a remote corner unreached, while a low-power unit placed on a relay path may unlock a longer chain. Reading power and position together is more useful than chasing the largest number on the board, and it is the difference between a single failed trigger and a clean five-field run.
Picking a Replacement Source That Covers the Field
Once the Tick recorder has shown you where the first wave stopped, choose the replacement source by reasoning forward in frontiers rather than by guessing. Mark the new source as tick zero, then list every uncleared unit inside its Manhattan range as tick one. From only that tick-one group, list which further units each can reach, and continue frontier by frontier until either every unit appears or the chain stalls again.
A few practical checks speed the search. Look for a source that reaches at least one useful relay, because a relay is what turns a short hop into a four-tick chain. A remote low-power unit is often the hardest endpoint, so verify which candidate can reach it before committing. Branches are valuable when they cover separate regions of the board, because a single source whose range spans two clusters can collapse several frontiers into one.
The five experiments progress from a short three-unit relay to longer fuses, a corner-to-corner handoff, a four-way bloom, and a final multi-branch surge. The grid size and the rules never change; difficulty grows through placement, power distribution, simultaneous waves, and directed reachability. Because the board is deterministic, every successful and failed trigger is fully verifiable, and you can compare your mental forecast with the exact recorded ticks to see precisely where a previous chain stopped.
When the new source clears the field, the failure history is wiped before the next level loads, so a single early mistake does not carry over into the later experiments. Independent tests lock the complete success set for each level and prove that every other source stops early, which means there is always at least one correct choice and the Tick recorder is reliable enough to find it.
Repair Rules at a Glance
These are the exact behaviours the game follows after a trigger fails, drawn from the product contract that governs scoring and repair.
| Action after one failed trigger | Result on the current field |
|---|---|
| Press the same failed source again | Counted as the same failed source; does not consume the second mistake. |
| Pick a different source that clears the field | Field awards 200 points; failure record cleared before the next experiment. |
| Pick a different source that also fails | Run ends; field awards no points; no further repair attempt allowed. |
| Run a successful corrected source after one failure | Failure history reset so the next level starts with a clean slate. |
Two more behaviours complete the picture. Independent tests verify that unit positions are unique on every field, that scoring is exact, and that restart equality holds, so leaving and re-entering a level leaves your progress untouched. Everything runs locally in the browser, and no account or network round trip is required to repair a failed trigger.