This is off topic, but I will follow-up upon what Fallenangle said...
Before I get to no damage itself, in the last few years, people have undertaken a challenge know as "no loads, no meds, all secrets" (nlnmas). A challenge which was thought to be impossible in TR3 without using the temperature bar exploit. However, it was found to be possible, though obviously quite difficult, demanding much practice. One mistake with the swim sequence and it's pretty much game over! About 6 people are on record for completing this challenge (for TR3) on Twitch/Youtube. In fact, all the classics have been done under these conditions.
As for no scratch/no damage (1HP challenge) or minimal damage, the last few months have seen things get taken to a whole new level. Eycore and a few others have been grinding away, testing out various strategies and exploits, culminating in successful runs (albeit with different rule sets) in TR1, Unfinished Business, TR2 Golden Mask and TR3 Lost Artefact. For these runs, the game exe is modified to always be at a value of 1HP. Meaning that any damage sustained throughout the run equals death.
Anyway, what I meant by different rule sets, is that currently, the runs are a mixed bag; most of the runs use glitches, but don't let that detour anyone who may think glitches are cheats and/or make the game easier because that is not the case at all. Glitched mechanics bring a whole new element of gameplay and skill, not to mention the fact that these no damage (1HP) runs are being played live, in a single segment without no saves whatsoever, with the exception of the save/load glitch (in glitched runs) which is used to despawn darts and lava embers, as these pose a huge threat in the latter parts of TR1. For glitchless TR1, an insane method to avoid the darts in the Great Pyramid was also found by Eycore. It requires a crazy
setup. Speaking of glitchless no damage runs, currently only
Unfinished Business and
TR3 Lost Artefact (both with secrets) have been completed. TR1 itself, without glitches is possible (with one instance of forced damage). It was attempted by Eycore recently, but unfortunately he died in Atlantis. Here are his
Twitch and
YouTube channel links.