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Item Generation Utils Methods
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remove_items_from_map
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Removes all items from the map. Is called before spawning a new wave of loot.

has_reached_item_cap
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Determines if too many of a type of item (gun, upgrade, money) spawns on the map and prevents another from spawning if there are too many.

pick_item
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Picks what item to spawn. 60% chance of money, 20% chance of a gun, and 20% chance of an upgrade.

place_item
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Places an item randomly on the map, will not spawn an item on top of another item. Items are placed on a standard distribution with the highest chance of spawning at the center of the map.