Currents strategy guide
Filling a grid with a single line is a routing problem, and routing problems reward structure over trial and error. Here is how strong solvers read a Currents board before the first drag.
Let the corners decide the route
A corner cell has exactly two neighbors, so a line that must visit every cell has almost no freedom there: unless the current starts or ends in that corner, it must flow in through one of the two sides and out through the other. Both edges are forced before you draw a single cell. Since the current always starts on gate 1 and ends on the highest gate, any corner that holds neither endpoint is a guaranteed through-turn.
Cells along the walls are nearly as constrained — three neighbors instead of four — and a wall cell whose two along-the-wall neighbors are already used becomes a dead end unless the current finishes there. Strong solvers sketch the forced corner and wall segments mentally first, then connect those fragments through the open middle of the grid.
Use the checkerboard argument
Color the grid like a checkerboard in your head. Every move the current makes steps from one color to the other, so a route through all the cells alternates colors the whole way. On a board with an even number of cells, the start and the end must sit on opposite colors; on an odd board, both endpoints sit on the color that has one extra cell. If gate 1 and the final gate do not respect that, no full-cover route exists — and our generator guarantees they always do.
The same parity logic works between gates mid-solve. The number of steps between two cells of the same color is always even, and between opposite colors always odd. If the stretch of unvisited cells you are about to sweep between gate 3 and gate 4 cannot match the parity of that distance, the plan is impossible — backtrack now rather than three gates later.
Never seal off a pocket
Your line is also a wall. Each new segment divides the board a little more, and any unvisited cells you close off behind that wall become permanently unreachable — the current cannot cross itself to get back in. The most common losing move in Currents is not a wrong gate; it is brushing along a wall and quietly trapping two cells in a corner behind you.
Before committing a segment, glance at the whole grid and ask what the move disconnects. If the unvisited region would split in two, the move is wrong unless one part is exactly where the current will end. This one habit — checking connectivity before speed — turns large boards from luck into logic.
Reason from both endpoints
You know both ends of the river before you start: the current rises at gate 1 and empties at the highest gate. That second fixed point is just as informative as the first. The final gate's neighborhood must stay open until the very end, so avoid spending all of its neighbors early — the current needs a way to arrive on its last step.
It often pays to solve a stretch backwards. Ask which cell must come just before the final gate, which cell before that, and so on — on constrained boards the last four or five links are frequently forced. Meeting in the middle from both endpoints shrinks the puzzle far faster than pushing forward blindly from 1.
Take forced moves before free ones
At any moment, some moves are choices and some are obligations. If the cell at the head of your line has a neighbor with only one remaining way in, that neighbor has to be served next — delaying it strands the cell. If two different neighbors are both down to their last exit, the position is already lost and it is time to drag back.
This is the local version of a global truth: a full-cover route exists only while every unvisited cell keeps at least two usable connections (or is an endpoint). Scan for degree-one cells after every few moves, handle them first, and spend your creativity only where the grid actually offers a choice.