AGK for Pascal
TAgkSprite.CategoryBits Property

Assigns the sprite to zero or more categories for collision filtering (physics and non physics).

property CategoryBits: Cardinal;

There are 16 categories, each represented by a single bit in the Categories property. A value of 1 for a bit represents that this sprite is a part of that category and 0 that it does not belong to that category. Sprites can then be set to collide with certain categories using CollideBits regardless of which categories they themselves belong to. 

By default all sprites belong to category 1 ($0001 the rightmost bit) and collide with all categories ($FFFF).

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