Marble race is a simple real life game in which marbles (small glass balls) are released onto a prepared track to race from start to finish by the force of gravity. This game is great because it is suckless, cheap (i.e. accessible), fun and has almost no dependencies, not even a computer -- such a game will be playable even after the technological collapse.
Even though this is a real life game, a computer version can be made too, in different forms: 2D, 3D, realistic or with added elements that would be impossible in real life, such as teleports. And indeed, there have been many games and mini-games made based on this form of entertainment.
From the implementation point of view it is very convenient that marbles are of spherical shape as this is one of the simplest shapes to handle in physics engines.
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