FruitFat is a catching game in which you react quickly to catch fruit before it hit the ground. You must catch fruit to gain points for your high score; if the fruits hit the ground, they will rot. Allowing the fruit to hit the ground in the same spot three times will lose the game. If you catch fruit consistently without hitting the ground, you will have a combo multiplier, and each fruit will grant two points instead of one.
 
Seeds fall from the sky and, when hitting the ground, will sprout a random tree. It is up to you to decide to catch the seeds or let them hit the ground, as hitting the ground increases the game's intensity as you juggle between more fruit falling from trees.
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Three different trees spawn from the seeds when hitting the ground, which grows different kinds of fruit. Each fruit type has a different reaction when falling from trees.
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There are also two large trees on each side of the game that have openings that you can bump fruit into like a soccer goal for points if you weren't fast enough to catch them with the acorn basket.
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Mole-like creatures will come and eat trees; you can allow them to eat trees or block them from doing so.
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If you plant three of the same type of tree, e.g., three apple trees, you will receive the ability to double-tap the screen and collect all of the fruit on the screen, going straight into your acorn basket.
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Every so often, a special seed will drop from the sky that you let hit the ground. It will grow into a special water flower with a water-based fruit that can be caught for points or allowed to hit the ground to remove rot from fruit hitting the ground.
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With all of this in mind, you try to position trees in places where you do not have much rot on the ground and control the number of trees you have by allowing moles to eat them or blocking them.

Strategically catching seeds that are falling in areas too wide apart increases the difficulty of going back and forth to catch fruit, or you let seeds drop close together, so it is easier to catch.
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FruitFat has two modes, normal and time attack. You can play normal mode infinitely until you allow three fruit to hit the same spot three times, losing the game. Time attack mode allows the player three minutes to gain as many points as possible before the timer ends or can lose by rotting the ground three times in the same spot.