Complex sentence: This limited the engine to polygon-based flat-shaded graphics, but at the time this was not uncommon, and with this engine many more polys could be drawn per-frame, greatly increasing visual fidelity.
Split into simpler sentences: This limited the engine to polygon-based flat-shaded graphics. At the time this was not uncommon, and with this engine many more polys could be drawn per-frame, greatly increasing visual fidelity.