+ colors = snewn(state->w * state->h, int);
+ check_complete(state, NULL, colors);
+ if (colors[(tile->y - 1)/2 * state->w + (tile->x - 1)/2]) {
+ sfree(colors);
+ return;
+ }
+ if (colors[(opposite->y - 1)/2 * state->w + (opposite->x - 1)/2]) {
+ sfree(colors);
+ return;
+ }
+
+ sfree(colors);
+ remove_assoc_with_opposite(state, tile);