Something I recently noticed about valve games is that their mechanics and gameplay niches are so ingrained into you if you play them long enough you tend to notice them in real life. I call this phenomenon valve sickness, to provide an example, if I play portal enough I start to see “portalable surfaces” everywhere. Any wall that’s colored white that is. Today I heard the squeak of someone’s shoe against the ground, and was the exact pitch and tone of the hunter noise cue from l4d, and suddenly got ready to be pounced for a second. Just something I found interesting.