Perfect is a Steam Achievement that requires you to complete a mission on Normal difficulty or higher without taking any damage.
- Pick your class and gear accordingly. You'll want to bring as much firepower as possible to take out aliens before they reach you. Wildcat, with her Speed Bonus, is an excellent choice.
- Don't bother equipping offhand items that increase your survivability (such as Heavy Armor or Electric Charged Armor). Instead, bring a Hornet Barrage or some Freeze Grenades.
- Friendly fire counts! Indeed, the greatest obstacle to earning this achievement is often not the Swarm, but other players.
- Soloing this achievement is possible, but takes time and a bit of luck. Landing Bay is not too difficult. Pick a Tech (Crash's skills are better suited for this) and bring the Flamer, an Advanced Sentry Gun, and some explosives (Trip Mines work well) for defending yourself during the computer hack.
- Sewer Junction B5 can also be soloed for this achievement. Pick Wildcat and bring a Flamer, a Tesla Cannon, and some Freeze Grenades. Set the Drones, eggs, Parasites and Buzzers on fire while disabling and running past the Shieldbugs.
- The name and picture for this Achievement is a reference to the Valve game Portal. One of GLaDOS's lines went as follows:
"Perfect. Now move quickly to the chamberlock."
- The picture is also a reference to Portal's ubiquitous "cake", which may or may not be a lie.