Temperature Cubes: +/- negative numbers

I've always struggled to give a hands-on situation for adding and subtracting negative numbers. I generally tend to focus pupils on the direction of movement (along the lines of: 'If you add or subtract with a negative number, then you move in the opposite direction to normal') along the number line. It has to be said, I dislike the 'magical' maths trick of 'If the signs are the same, then add; if the signs are different, subtract.' Partly because maths really isn't a system of rules to remember, and secondly because pupils then become mightily confused when you give them the next magical maths trick (when multiplying / dividing) of: 'If the signs are the same, the answer is positive; if the signs are different, the answer is negative.'
So here is an attempt to instead give them a situation to play around with, where the effects of adding / subtracting negative numbers can be seen more readily (I hope!)