He's gone to bed, but I'll do you the favor of an indepth explanation. I won't bother with screenshots, but I'll use this to explain.
Basically, there are two different types of game modes. You have
Mono where there is two different blocks (cars, from here on). You have your grey, and your multi-coloured cars. In Mono, all you need to worry about is hitting the multi-coloured cars, and NOT hitting the grey cars. I would suggest you play this mode until you're familiar with the game mechanics.
Then, you have the mode with many different colors of cars. Purple, blue, green, yellow, and red. The casual modes (Pointman, and Double Vision) have blue, yellow, and red. The pro modes (Vegas, Eraser, Pointman Pro, Pusher, and Double Vision Pro) have purple, blue, yellow, and red. Finally, the elite modes (Eraser Elite, Pointman Elite, Pusher Elite, and Double Vision Elite) have purple, blue, green, yellow, and red.
Essentially, in all of these modes you are simply attempting to collect three or more colors in a row. This can be done in many ways. I'll draw a few diagrams here. Imagine the X's as a single color, and the O's as another color.
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X
XX
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X
XX
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XX
XO
In all three of these cases, the X's would disapear after a few moments, and give you points. This is the basic concept behind the majority of the game. The seperate game modes will then give you different abilities (which are described in-game) that allow you to manipulate the cars to your advantage (IE: pusher can push a car to the left or right side, pointman can pick up a car and then drop it somewhere else, etc.).
Hopefully this helps you understand a little better.
Additionally, the "stacks" are at the bottom, underneath your character. They're represented by empty boxes, until you hit a car, then that car goes into its column and sits there as whatever color it was until it can match with another 2 of the same color, as shown above.
