Lamarr is the reason HL2 is HL2. If she didn't interfere with the teleportation: 1. Freeman goes straight to BM East, so Route Kanal and Water Hazard are skipped. 2. Combine didn't have time to invade BM East so quickly, so Eli isn't captured and falling debris doesn't separate Freeman from Alyx, and Freeman doesn't have to rescue Eli from Nova Prospekt. Ravenholm, Highway 17, Sandtraps, Nova Prospekt, and Entanglement are skipped. 3. Nova Prospekt doesn't blow up, so uprising doesn't start and they probably plan some better and sneaky ways to defeat the Combine in BM East. It probably goes much easier than the whole uprising and breaking into the Citadel. All chapters beyond Entanglement are skipped. 4. So basically game consists of only Point Insertion, Red Letter Day, Black Mesa East and some tasks after BM East.