My 8-bit games just used rectangles; for circles I just overlapped two inside the geometry in a fat "+" shape. This was on a platform with pixel-accurate collis

My 8-bit games just used rectangles; for circles I just overlapped two inside the geometry in a fat "+" shape. This was on a platform with pixel-accurate collision detection in hardware, and I always thought that the sloppy geometry-based detection was more fun for players. N-squared for single-digit N worked just fine, too.