Planks are the currency in Stair Race 3D. You dash around an arena gathering them, then spend them by laying down a staircase that carries you up to the next platform, while rival runners are trying to do exactly the same thing.
It comes down to who carries more. If your pile of planks is bigger than theirs, you knock them over and gain the advantage, so check the size of their stack before you charge.
Building early gets you higher sooner, but a thin pile also makes you an easy target. Collecting a healthy stack first keeps you safer when the arena gets crowded.
Yes, character skins and different plank styles. The 3D levels run on desktop and on phones. For more climbing toward the top of a map, Only Up Parkour is a natural next stop.