generate_sum_grid = function()
	-- a sum grid is fully characterized by 4 numbers
	Char = {
		data = {
			{ math.random(1,9), math.random(1,9) },
			{ '', ''},
		},
		row_totals = { '', '' },
	}
	Char.col_totals = {
		math.random(Char.data[1][1]+1,10),
		math.random(Char.data[1][2]+1,10)
	}
end

create_problem = function()
	local s = Solution
	Problem = {
		row_totals = {s.row_totals[1], s.row_totals[2]},
		col_totals = {s.col_totals[1], s.col_totals[2]},
		data = {
			{'', ''},
			{'', ''},
		},
	}
	local x = math.random(1, 2)
	local y = math.random(1, 2)
	Problem.data[y][x] = s.data[y][x]
end

new = function()
	generate()
	solve()
	create_problem()
end

generate = function()
	-- a sum grid is fully characterized by 4 numbers
	Char = {
		data = {
			{ math.random(1,9), math.random(1,9) },
			{ '', ''},
		},
		row_totals = { '', '' },
	}
	Char.col_totals = {
		math.random(Char.data[1][1]+1,10),
		math.random(Char.data[1][2]+1,10)
	}
end

		generate_sum_grid()
		solve()

		new()

	new()