Connect up the tiles so that each number has it's own group containing the specified quantity of tiles.
The group must contain the number, e.g. the 3 must contain the "3" tile and two other adjacent tiles.
Tiles can only connect horizontally and vertically, not diagonally.
todo:
fix validation so you can't have isolated cells. currently it works off the cell count rather than connections
then create a solver program to find all the good puzzles. so far they're all really easy with multiple solutions.
then make tile sets that pick the right tile based on 9 possible values.
make it work on mobile with touch input