* below it might form a <-shape between them
*
* Any starting 1 or 3 clue rules out four bits in this array
- * immediately; we can rule out further bits during play using
+ * immediately; a 2 clue propagates any ruled-out bit past it
+ * (if the two squares on one side of a 2 cannot be a v-shape,
+ * then neither can the two on the other side be the same
+ * v-shape); we can rule out further bits during play using
* partially filled 2 clues; whenever a pair of squares is
* known not to be _either_ kind of v-shape, we can mark them
* as equivalent.
memset(sc->vbitmap, 0xF, w*h);
/*
- * Initialise the `exits' and `border' arrays. Theses is used
+ * Initialise the `exits' and `border' arrays. These are used
* to do second-order loop avoidance: the dual of the no loops
* constraint is that every point must be somehow connected to
* the border of the grid (otherwise there would be a solid