Complex sentence: Placed in direct competition with "Microsoft Flight Simulator 2000" and "Fly!", the game became one of Looking Glass's biggest commercial flops, with roughly 20,000 units sold in the United States during 1999.
Split into simpler sentences: Placed in direct competition with "Microsoft Flight Simulator 2000" and "Fly!", the game failed to capture sufficient market share. It became one of Looking Glass's biggest commercial flops, with roughly 20,000 units sold in the United States during 1999.