1: Yes, setting the time isn't a modification of hardware.

2: No, because then you could just give yourself hacked items (items are based on their item seed) to one-shot Diablo. Where would the limit be if save editing were allowed? Why go down all the stairs when you could just change your current level to the last one by editing the save?

3: The rules are guidelines for what you can expect your run to be rejected for, not an exhaustive list. The discrepancy is probably just a case of the rule specifically targeting issues that have come up, while the summary simply states that, in general, any modification is not allowed. I don't see the conflict, just apply both. After all, if you were allowed to mod the game, you could just make the win condition talking to Pepin when you first enter town, and now you can beat the game in a few seconds.

> The implication is that there is some form of RNG manipulation in Diablo 1 that would have been allowed, but the actual form of manipulation that groobo used wasn't it. If that's true, the article should have covered what would have been allowed and why this was different. As written, this looks more like the journalist didn't bother reading what groobo said about his video.

The simple rule is that you can use any manipulation as long as it relies only on the game itself. This includes starting the game at a specific system time.

Some of Groobo's claims are simply impossible to achieve through RNG manipulation in Diablo. For example, item drops are predetermined at game start and are not influenced by the runtime RNG. The only way to alter them would be by using a tool to modify the game’s memory. In one of his older videos, such a tool can be seen running in the taskbar. He also admits to using one to skip through levels while searching for a good level set to run. While that isn't a problem in itself, the tool must be off during the actual run.
Evidently, it wasn’t off for the final fight, and that's also the only plausible explanation for the item drops seen during the run. If he knew of a legitimate way to manipulate drops, he could simply explain it to clear things up.

This TAS demonstrates a lot of what can be done within Diablo's mechanics:
https://www.youtube.com/watch?v=tiwoqd4arI0
- Boot the game at a specific point after Windows startup to get a perfect shop.
- Enter a new game at a specific system time to generate ideal levels.
- Split gold to manipulate RNG.
- Wait for the monster AI to advance RNG.

For full details on all tricks used, you can read this article: https://tasvideos.org/9396S

> While there isn't an explicit continuity requirement in 2009, the difference between fighting a boss at level 26 vs level 12 is large enough that I'm comfortable assuming it violated an implicit requirement. I'm also curious about whether your level is displayed on screen - which would imply that the video isn't just segmented but assembled from edited frames - or not. This finding appears to have been glossed over because it's not in the original report on the video. But the journalist should have exercised better judgment.

The level is only shown when opening the character panel, which does happen a few times. However, you can also estimate the level based on the amount of mana consumed by spells. He is evidently level 12, but his damage output matches that of a level 26 hero. Most likely, this was achieved by modifying the base damage formula used to calculate fireball damage.

If you check the source article, you can watch a recreation using an unmodified game with a level 12 hero, where the fight desynchronizes, and the hero dies. In contrast, when fireball damage is artificially enhanced, the gameplay remains synchronized throughout the fight.

https://diablo.tas.bot/#Artificially_Enhanced_Fireball_Damag...

From what I understood, Groobo had come to the understanding that 19 fireballs would have been enough with perfect RNG based his calculations using number from various strategy guides.

A lot of what happens in this run can be explained as him simply wanting to create the perfect run but making bad assumptions regarding what could actually be done legitimately and ending up with an impossible run instead.