Fill every empty cell so each row, column and box holds every digit once: 1–4 on the 4×4, 1–6 on the 6×6s (boxes are 2 rows × 3 columns) and 1–9 on the 9×9. Tap a cell, then a digit, or tap a digit first and then the cells it goes in. Tapping a number highlights every matching number on the board. Turn on Pencil to jot notes; notes clear themselves when that number is set nearby.
Flow: set a right number within 6 seconds of the last one (6.5 on the 9×9) and Flow goes up by one, to ×6. The ring round the digits shows the time left. Every number and every finished row, column or box is multiplied by your Flow, so look for the number that unlocks the next one and set them in a chain.
The clock: one clock runs for the whole run. Each right number adds 2 s, each finished row, column or box 3 s, and each solved board refills it for the next. A wrong number costs 8 s and 100 points and ends your Flow. Four wrong numbers on one board, or the clock running out, cost a lamp: the board fills itself and you go on to the next. Lose all 3 lamps and the run is over.
Lantern (once per board) lights a cell you can set right now, for −15 s.
The boards: a 4×4 warm-up, a 6×6 that falls to "only one place for this digit", one that needs "only one digit left for this cell", one that needs a pair, and a 9×9 finale. Every board has one solution you can reach by logic alone.
Scoring: 30 × Flow per right number, 120 × Flow per finished row, column or box, 300 × the board number per solved board (doubled with no wrong numbers and no Lantern), and at the end 10 per second left on the clock if every board was solved, plus 1,000 per lamp left.
Keys: 1–9 to place, arrow keys to move, P pencil, L Lantern, Backspace clears notes, Esc pauses, M mutes, Enter presses Play.
