Negativity

I made this game for #60minutejam - drag numbers together to multiply them. When they hit the bottom of the screen, they'll add or subtract to your total score, depending on if they're negative or positive. 

In higher levels, numbers can be multiplied more than once, yielding higher and higher scores.

The game ends when you get bored.

BUG: you're supposed to be restricted to multiplications by your level - you should only be able to multiply a number with another number if it's not locked, and it should be locked after it's the product of one or more numbers that... whatever, it's a glaring bug, but I'm not fixing it.