function stateGame()
	local board = Board.new()

	local selectedId = 1

	local function drawSelectedTile()
		local x, y = board:draw_coords(selectedId)
		local w = board:getTileWidth()
		rect2(x-1, y-1, w+2, w+2, 6)
	end

	local function create_board()
		printh("a: " .. time())

		repeat
			board:reset()
			repeat
				board:solveStep(true)
				yield()
			until board:isComplete()
		until board:isValid()

		printh("b: " .. time())
		-- Remove tiles until randomness is unavoidable
		local previous = {board:getTilesCopy()} -- initial state
		local invalidcount = 0
		while true do
			board:setTiles(previous[#previous])
			-- remove a random tile
			local i = board:getRandomNonZero()
			board:fill(i, 0)
			add(previous, board:getTilesCopy())

			-- try to solve the board
			local solved = ""
			yield()
			repeat
				solved = board:solveStep()
			until board:isComplete() or solved == "invalid"
			if board:isComplete() then
				invalidcount = 0
			end
			if solved == "invalid" then
				deli(previous)
				invalidcount += 1
			end
			if invalidcount > 50 then
				break
			end
		end -- end while
		printh("c: " .. time())

		board:setTiles(previous[#previous])
		printh(board:tostring())
		printh(count(board:getTilesCopy(), 0).." zeroes")
	end

	local function _enter()
		local c = cocreate(create_board)
	end

	local function _draw()
		cls()
		board:draw()
		drawSelectedTile()
	end

	local function _update()
		local size = board:getSize()
		local x, y = board:idx_xy(selectedId)
		if btnp(UP) then
			y -= 1
		elseif btnp(DOWN) then
			y += 1
		elseif btnp(LEFT) then
			x -= 1
		elseif btnp(RIGHT) then
			x += 1
		end
		if (x<1) x=size
		if (x>size) x=1
		if (y<1) y=size
		if (y>size) y=1
		selectedId = board:xy_idx(x, y)
	end

	return {
		_enter = _enter,
		_update = _update,
		_draw = _draw,
	}
end