What is a small black bug shaped as a circle?

A small black bug shaped like a circle could be a type of beetle, such as a ladybug or a pill bug (roly-poly). Ladybugs are often round and have a glossy appearance, while pill bugs are more oval but can appear circular when curled up. Another possibility is a black fungus gnat, which is small and may appear round from certain angles. Identifying the bug more accurately would require additional details about its size, habitat, and behavior.