Sudoku

Sudoku in the panel, made on your machine. Enter on the palette's row opens the board as a view level whose body is the extension's own page (surface/, a surface view node): the board, and beside it a slim side with the clock, a line filling as the cells do, a pad of slim keys (a bar under each digit for how many are down) and one row of tools.

The page imports the rules from game.ts and the solver from sudoku.ts, the same files the host tests use, so it draws and takes input but never decides a rule. Every move goes to the extension (pal.send), which keeps the game in progress.json, so Escape anywhere loses nothing.

• Puzzles: a daily for each of Easy, Medium, Hard and Expert, made from the date (the same on every machine that day), and a new one of any difficulty on ⌘N. A full grid is filled at random, clues are taken away in mirrored pairs while the answer stays unique, and the result is solved the way a person would and graded by the hardest technique it needed: singles you can spot (Easy), a cell with one digit left (Medium), locked candidates, pairs and triples (Hard), X-wings, swordfish and XY-wings (Expert). A puzzle of the wrong grade is thrown away and another made; an expert one takes a few dozen tries, about 30 ms.
• Notes without an extra step (game.ts enter): a different digit typed over one you placed turns the cell into notes holding both (j marks the cell), and digits toggle notes there until Backspace clears it. With check = "mistakes" a wrong digit is replaced and a right one stays. Shift or Option with a digit, or N (Space) for notes mode, as before; on the pad a click places, a right-click, ⌥-click or the key's corner writes the note. Notes sit in a 3 by 3 in the cell; a placed digit clears its note from the cells it sees. A fills every note in, Shift-A clears them.
• Auto notes (C, auto_notes = true): a second layer. Every empty cell shows what fits, less what you took out (x, kept per cell, so a removal survives the board changing); your own notes (n) stay underneath for when it is turned off. marks(p, auto) is the layer on show; each move takes auto and writes only that layer.
• Digit first (D): pick a digit, the cells it fits in light up, a click places it (a note in notes mode). Enter places at the cursor, Tab goes to the next lit cell, D leaves.
• Clarity: clues solid, your digits in the accent colour; the cursor's row, column and box lit, its digit lit everywhere and that digit's notes circled; a clash is a red line under your digit with the clue it runs into ringed (every mistake in red with check = "mistakes"); a sweep of light for a finished row, column or box.
• Hints (I): where to look, then why in plain words, then the move.
• Undo (U, ⌘Z) and redo (Shift-U, ⌘⇧Z), erase (Backspace, 0), Tab to the next empty cell, arrows or hjkl, clicks on the cells and the pad.
• The clock runs only while the board is on screen; P pauses it and covers the board. T (or clock = false) hides it for anyone it rushes: no time on screen while you play, though the time still counts for the stats and shows on the finish.
• Browse (⌘O): every half-done game and a calendar of dailies per difficulty. Stats (⌘S): best and average time, the streak, a chart, the history, per difficulty.

Files: sudoku.ts (solver, generator, grader), game.ts (moves, marks, the saved form, the hint), stats.ts, store.ts, index.ts (the extension's calls), surface/ (the page; screens.ts Browse and Stats, fx.ts the confetti).