You might find this funny https://wiki.sourceruns.org/Infinite-Health-Door.html https://wiki.sourceruns.org/Infinite-Health-Door.html In Half-Life 1 there is

You might find this funny https://wiki.sourceruns.org/Infinite-Health-Door.html https://wiki.sourceruns.org/Infinite-Health-Door.html In Half-Life 1 there is a map with two doors that deal negative crushing damage, so you can wedge yourself in them to give yourself a massive over heal