Sum Stacks - play online

At the top of the screen are several target numbers. Use red, green, yellow and purple numbers to make each target number. Each color corresponds to a different mathematical operation. If you drop a number of one color onto another, the mathematical operation of the discarded number is used (so if you move x3 to +2, the answer will be 6, but if you drop +2 to x3, the answer will be 5.) The puzzle is only solved when all the numbers used. Use the mouse to match the numbers.