Double Impact

Double Impact is a episode replacement PWAD for The Ultimate Doom by Matt Cibulas (RottKing) and Ralph Vickers (Ralphis). It is a winner of 2011's 18th Annual Cacowards, requires a limit-removing port to play. In its original PWAD form, it replaces all nine levels of Episode 1. It has also been included with Freedoom: Phase 1, as part of the fourth chapter of the game.

PWAD line-up

 * E1M1: Maintenance Area
 * E1M2: Central Computing
 * E1M3: Research Complex
 * E1M4: Hydroponic Facility
 * E1M5: Engineering Station
 * E1M6: Command Center
 * E1M7: Waste Treatment
 * E1M8: Launch Bay
 * E1M9: Operations

Freedoom line-up

 * C4M1: Maintenance Area
 * C4M2: Research Complex
 * C4M3: Central Computing
 * C4M4: Hydroponic Facility
 * C4M5: Engineering Station
 * C4M6: Command Center
 * C4M7: Waste Treatment
 * C4M8: Launch Bay
 * C4M9: Operations

The Freedoom versions of the levels are largely identical, with the major difference being that M2 and M3 are swapped to facilitate the secret exit.