While messing around with Portal 2 I noticed that anything higher than 2x AA kills fps if looking at a portal while OBS is open. I also always open task manager and give hl2.exe a higher cpu priority. That pretty much fixed 99% of all fps drops I had.
Are you in full screen or windowed mode ? Full screen fix lag usually. Also what's your specs ?
If you are launching the game through steam you aren't playing on the source unpack version. You have to use the batch file. Try using windows 10 game mode?
Oh, did you put the game in steam directory ? because you have to not do this. Just extract it and launch it with the bat. Did you try to play with your game in an other hard disc ?
Inbounds runs that use Item Save Glitch to perform 02 skip will now be accepted to the leaderboards. Please provide demo proof for any such runs.
