Sprite Class constants
Each of the sprite class has an ID (integer) associated with it. You can use these constants:
CLASS_BACKGROUND_DECORATION CLASS_ANTIGRAVITY CLASS_METAL_LADDER CLASS_SOLID_DOWN_ONLY CLASS_REVERT_TO_BACKGROUND CLASS_IMMEDIATELY_DEADLY CLASS_SOLID_BACKGROUND CLASS_STOP CLASS_ANIMATED_THING CLASS_PICKUP_TRIGGER CLASS_INVENTORY_ITEM CLASS_OPEN_TO_OWNER CLASS_TELEPORTATION_PAD CLASS_TELEPORTATION_DESTINATION CLASS_Z_KEY_SWITCH CLASS_ANIMATE_ONCE CLASS_SOLID_ANIMATED CLASS_PLAYER_OBJECT CLASS_GENERIC_MONSTER CLASS_USER_DEFINED_MONSTER CLASS_DRONE_UP_DOWN CLASS_DRONE_LEFT_RIGHT CLASS_ATTACKER CLASS_VAMPIRE_PLANT CLASS_WHACKER_UP_DOWN CLASS_WHACKER_LEFT_RIGHT CLASS_PLATFORM_UP_DOWN CLASS_PLATFORM_LEFT_RIGHT CLASS_PLAYER_BULLER CLASS_MONSTER_BULLET