The controls.
Moving. Tap or click a burrow to select it. Drag across the meadow, with a finger or with the mouse held down, and every burrow you cross joins the selection. Ctrl, on a Mac Cmd, plus a click adds one burrow to the selection or takes it out again. The arrow keys, or W A S D, move the selection and wrap round the edge, so down on the last row comes back to the top; Ctrl plus an arrow widens the selection instead of moving it. Escape lets the selection go. A burrow the meadow gave you can be selected, so you can put marks and colours around it, but it can never be overwritten.
Writing. The keys 1 to 9, the numeric keypad and the pad under the meadow all do the same thing, and they write into every selected burrow at once. The same number again takes it back. Delete and Backspace clear in one order: if any selected burrow holds a big number, the big numbers go; if not, the marks of those burrows go, corner and centre together; if there are none, the colour goes. A number written into a burrow that already carries marks simply covers them, it does not lose them: take the number out again and every mark is back.
Four modes. The four buttons under the pad say what a number writes. Normal is the big number. Corner is a small mark in the corners of the burrow, filled in the same order every time, left top, right top, left bottom, right bottom, then top, bottom, left, right and the middle. Centre is a small mark in the middle, kept in order. Colour paints the burrow with one of nine colours; every hued colour also has its own texture, so no two are told apart by hue alone, and the first colour is the plain neutral one. The keys Z X C V pick a mode, the spacebar cycles through all four, N goes Corner, Centre, Normal, and holding Shift borrows Corner or Ctrl borrows Centre for as long as you hold the key down.
Undo, Redo and Restart. U or Ctrl+Z go back, R, Ctrl+Y or Ctrl+Shift+Z go forward, as far as you like and through everything, numbers, marks and colours alike. Ctrl+R stays your browser's reload; we never take that one. Restart puts the meadow back to the numbers it was given and clears everything else, colours included, and one Undo brings it all back. The clock keeps running through a Restart: clearing up is part of playing, not a new game.
Check. Press it once and it says how many numbers are wrong and roughly where; press it again and it marks them. With exactly one burrow selected it reads only that row, that column and that block. Nothing else on the board ever turns red while you play.
Settings under the meadow hold the rest: which comes first, the burrow or the number; the timer; highlighting matching numbers; whether a drag selects several burrows; what a number does in a burrow that already has marks; whether errors are shown at once; corner or centre as the default mark; whether writing a number takes that mark out of the burrows it rules out; the automatic pause; input from the pad only; and whether Restart asks first.
