1. 'Lambda Locator'
Description: Find all 45 Lambda caches. These are hidden supply stashes marked with the Lambda symbol. Requires thorough exploration of every chapter.
2. 'Gotta Kill 'Em All'
Description: Kill every Antlion in 'Sandtraps'. This is a challenging achievement that requires you to actively seek out and destroy every Antlion nest and individual Antlion in the chapter.
3. 'Revenge!'
Description: Destroy the Hunter-Chopper in 'Water Hazard'. This is a story-related achievement, but it's still a significant milestone.
4. 'Zombie Chopper'
Description: Get through Ravenholm using only the Gravity Gun and Crowbar. This is a challenging playthrough, forcing you to master environmental kills and melee combat.
5. 'What Cat?'
Description: Break the teleport in Kleiner's lab. This is a story-related event in 'A Red Letter Day'.
6. 'Blast from the Past'
Description: Find the HEV Suit charger in Black Mesa East. This is a small, easy-to-miss detail in the facility.
7. 'Pacifist'
Description: Don't kill any Combine soldiers in 'Point Insertion'. This requires careful stealth and evasion in the first chapter.