Route Plan

Twenty-five numbers sit in a five-by-five grid. You start on the top-left tile and you are heading for the bottom-right one, moving only right or down, and every tile you stand on adds its cost to your total — including the one you start on. The grid asks for one thing: arrive on exactly the stated total, not under it and not over it. Nine tiles, eight steps, and seventy possible ways across. Each grid is built around a route that already works, and every other route reaching the same total is counted before you see it, so the game can tell you how rare your answer was.

It runs entirely on your device: 0 network requests, works offline. No ads, no account, nothing to buy, and no betting, money or prizes of any kind.

1. Read the target above the board. It is the total the whole route must come to, and it never changes for that grid.
2. Focus the board — click it, or press Tab until it is focused.
3. Step right or down with the arrow keys, or with D and S. The tile you are standing on is outlined, not just tinted, and every tile you have walked prints the total you had spent by the time you reached it — =17.
4. Keep going with Enter, which repeats whichever way you last went. Handy on a long straight run; it starts out going right.
5. Read the two steps in front of you. A step you may take prints what you would still need after taking it — →9 means nine left to find. A step marked over cannot get you there because every route on from it passes the target, and one marked short cannot because no route on from it ever reaches it. Both are worked out from the cheapest and dearest finishes still reachable through that tile.
6. Step back for free with the left or up arrow, or Z. Press Esc to go back to the start, or click any tile you have already walked to rewind straight to it. None of that costs you anything.
7. Mind the last step. Stepping onto the finish ends the attempt — that is the one commitment in the game. Land on the target and the round is won; land anywhere else and it costs one attempt and puts you back at the top-left corner.
8. Watch the attempts. A grid with a single route gives you five, a crowded one three. Run out and the round ends, and one route that would have worked is marked on the grid.

How do you find a path across a grid that adds up to an exact total?

Stop adding forwards and start ruling steps out. For every tile you can work out the cheapest and the dearest finish still reachable through it — take the better of its two onward steps all the way to the corner for one, the worse for the other — and that pair is a band. If the target sits outside the band, no route through that tile can ever hit it, so the step is dead before you take it and half the grid can go with it. Route Plan does that arithmetic for you and stamps the dead steps over or short, which is the whole skill the game exists to teach: interval reasoning beats running totals, because a running total only tells you where you are, while a band tells you where you can still get to. The catch — and it is the reason the grid is still a puzzle — is that a band is a necessary condition, not a sufficient one. The totals actually reachable through a tile are full of gaps, and the band is only their outer edges, so a step marked →9 can still dead-end a few tiles later. Prune with the band, then search what is left, and step back the moment both ways forward go dark.

Is every grid actually solvable?

Yes, and by construction rather than by luck. The route comes first: the generator shuffles four right moves and four down moves — any shuffle of that set walks from corner to corner without ever leaving the grid — gives those nine tiles their costs, and the target is their sum. An exact route therefore exists before a single other tile has been filled in, and filling the rest can only add more routes; it can never remove that one. The finished grid is then handed to a separate counter that walks all seventy monotone paths and totals each one. It never looks at the route the generator planted, so finding at least one is a genuine check rather than an assumption, and the route revealed when you run out of attempts is the one it found. The test suite runs that check over thirty seeds, and also proves the counter walked exactly seventy paths every time.

Why is one grid worth more points than another?

Because the game knows exactly how many answers each grid has. Seventy paths of nine tiles is 630 additions, so there is no sampling and no shortcut — every route is walked and the ones hitting the target exactly are counted. That number is shown to you as Routes, and it drives everything: a grid with one route pays eight times what a grid with eight routes pays, and it also hands you five attempts instead of three. Difficulty here is measured from the solver's own work, never guessed by a designer. The generator draws up to six grids and keeps the one with the fewest routes, so scarce grids are hunted for rather than waited for.

Can I just follow the marks and never think?

No, and that is deliberate. The marks are sound — a step a real answer goes through is never stamped over or short, which the tests check on every seed, so trusting them can never cost you the grid. But they are not complete: across thirty seeds roughly one in eight of the steps offered as playable leads nowhere, because the band only bounds the reachable totals rather than listing them. Following ticks blindly walks you into a dead end often enough that backtracking is a normal part of the game rather than a punishment — which is exactly why stepping back is free everywhere and only arriving at the finish commits you.

Is there any money, betting or in-app purchase in this?

None, and there never will be. The numbers on the tiles are costs in the arithmetic sense — what a step adds to your total — and nothing else: no currency, nothing to buy, no wager of any kind, and no gambling mechanic anywhere in the game. The score exists so that a scarce grid is worth more than an easy one, and it buys nothing.

Does it work offline?

Yes. Once the page has loaded once, the whole game is on your device — the grid generator, the route counter, the band solver, the rules and this copy. Nothing is fetched while you play, and no result ever leaves the device.

Can I play it with a keyboard or a screen reader?

Both, and with the same rules rather than a reduced set. Arrows or WASD step and step back, Enter keeps going, Z takes one step back, Esc restarts the route. Every tile announces its cost and what it can do right now — "you can step here, leaving 9 to find", "you can step here, but every route on from it passes 41", "on your route, tile 4, 23 spent by here" — and the board announces the target, what you have spent, what is left, the whole band of finishes still reachable from where you stand, what each of the two steps in front of you would cost, and how many attempts remain. Nothing anywhere depends on telling one tint from another.

Five by five, costs of 1 to 9, and routes of exactly nine tiles moving only right or down — diagonals and backward steps are not moves in this game, so a route can never revisit a tile and there are always exactly seventy of them. Every grid is drawn up to six times and the scarcest kept, so most have one to four routes; the counter is exhaustive rather than capped, because seventy paths is cheaper to walk than to approximate. Stepping is free and reversible everywhere except onto the finish, which is judged the moment you arrive. There are no hints, no timer and no undo history beyond rewinding the route you are on.

Sum Links is the other arithmetic search on a grid — trace touching numbers to a stated total — and it verifies every board before you see it, exactly as this does. Target 24 is the same idea without a grid: four numbers, four operations, one total, every hand checked before it is dealt. Knight Hop is the other game about committing to one path across a board. Grid Clues and Mini Sudoku are the two here that are purely about eliminating what cannot be true, which is the same move as reading a band.

Bookmark this page (Ctrl+D, or ⌘D on Mac) or install the app — it works offline the next time you need it.