yeah, portal 1 and 2 are both pretty low spec requirements. both quite old based on the source engine used for HL2. pretty much playable at over 60fps on most current bottom-end onboard intel integrated intel GPUs at like 2k resolution

and yeah, idk about 3 hours, maybe, if you have a walkthrough guide. the storyline is pretty hilarious. the AI goes psychotic of course, in both episodes