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Comment by ktpsns | Hacker News Reader

The Broodwar replays were really cursed -- I remember that hilarious (perfectly reproducable) bugs of quickly replaying a game which resulted in a completely different replay then the actual game, apparently because the replay missed to integrate all replay information correctly and ended up in a different game state.

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Most of game corruption wasn't the result of faulty replay save / generation. Most of game corruption was the result of replays only recording user actions, and when the game engine was patched and rules were changed, re-playing the same user action could go wrong: imagine the cost of Probe getting increased from 50 minerals to 60. You load a replay that contains a "Build Probe" command when the user had 50 minerals. In the new game engine no probe will be built as the player does not have enough minerals. If this new probe was used to build other buildings, those also will not be built in the new game engine. Butterfly effect.

> imagine the cost of Probe getting increased from 50 minerals to 60

Yes, please.

- T, Z

Artosis alt account?! :P

60 mins, 15 gas and a forge.

This brings another question, if I watch an old replay, does it mean it has to have the versioned game engine stored in the computer? Does it mean with every update it gets increasingly bigger? Or is there a number of supported versions you could replay? I only started playing like 3 years ago...

SC2 patches to an older version if you load an old version. Then patches back to current version when you want to play again. It requires the game to restart -- and while SC2 has a feature where you can watch a live replay with your friends (by all joining the same game which is hosted as type "replay") -- that "watch replay with others" feature only works with replays which were created in the latest version because only the latest version of the client can connect to the multiplayer servers.

I'm not sure if the older patches are hot-downloaded on-demand when you load an old replay, I think they actually might be -- but I don't know.

You can also "resume" a replay from any point and you and a friend can take over the game from that point. I think Harstem (both a professional player and a big streamer/ YouTuber) has a few YouTube videos where he explores a famous game where one pro player "had clearly lost and had absolutely no chance to win" but the losing player stayed in the game for a really, really long time and people were talking about whether and to what degree that was "unsportsmanlike" (similar to not resigning in a clearly-lost chess game). Harstem would take the losing side at the point in time that was generally agreed to be "lost" and some of his viewers of various ability levels and IIRC he beat all of them.

Wow that is interesting that it patches back and forth, super cool! How did you find out about this? I wonder now and then if one can "consume" the events on a live game somehow, like connect as a bot or sniff the events before they are encrypted through the network... Also curious about the drone kill counter mod/overlay that Harstem uses, do you know of the name of that? I can't figure it out but would love to enrich it with stats from the data analysis

> How did you find out about this?

I studied SC2 altogether far, far, too much from 2019-2022. Had a goal to get into masters, played tens of thousands of games, watched multiple YouTube videos every day, memorized and practiced dozens of build orders, but still got stuck at my peak in low diamond.

When you're playing that much and reviewing replays, you start wondering why you can't watch old replays with people coaching you and someone eventually ends up explaining the system to you.

> sniff the events before they are encrypted through the network

Uhh, this is confusing as written. But there are cheating hacks which allow you to see extra data that is sent to your client in-game, such as the entire map and your's and your opponents production queues. And while I'm not sure if this is what you were asking: "sniffing" events from other clients which haven't been sent to the blizzard server is not possible, because they're delivered to your client via the blizzard server (it's not P2P).

> Also curious about the drone kill counter mod/overlay that Harstem uses, do you know of the name of that?

It's a combination of two things: 1) A customized UI layout for replays called "GameHeart" and 2) a custom SC2 game mod called "GameHeart" -- you can use the UI layout for ladder games which weren't created as custom games with the GameHeart mod, but for that replay you'll miss out on features like the drone kill counter and income graph vs. time for which the data is generated by the game mod.

Can you link to any of those Harstem videos where he takes over the "losing" side?

I cannot. Perhaps I'm misremembering some details -- but I cannot even find any YouTube videos where a strong YouTuber resumes replays to play out with other people. So no matter which details I have right/wrong, I'm unable to find the video.

I swear I've seen the same video(s). I couldn't find after a brief search either but there's something like this he did.

Exactly. Divergence is immediate and you wasted your high waiting for something to happen, only to discover that replay was generated by another game version. There was no youtube at the time and downloading replays was the only option and the good players weren't exactly thrilled to share them.

Btw such move instructions I visualize here with the amazing rerun.io https://sebosp.github.io/swarmy/public/0.5.1/2023-GSL-S1-RO1...

I fantasize if training an AI to watch all the replays of a map on YouTube can create a repro of the state machine logic that moves the units through the game, or to find the parts of a map that cannot be walked upon. In the replay it emits an event when the user wants a unit to move to x, y but then it has to path its way there, and I cannot predict (without their logic) how it would move there

The same can happen in a live game. Apparently LAN games don't check for consistency in game state so you can just diverge over time. One of the observers in ASL desynced in the RO8 just the other day so it travelled over into remastered.

This isn't a deficiency of LAN games, it's a deficiency of the observer mode Blizzard added to the game when they remastered it. The code they wrote to deal with stealthed units as an observer mistakenly changes the actual game state when you change player vision (i.e. set the game to only show one player's vision), which leads to the game state desyncing for the observer that does this. I run a project (ShieldBattery) where we've developed numerous patches to the game including a fix for this bug, but pro games don't use our stuff so they're stuck with the bug unless Blizzard decides to maintain the game again.

Oh, that's good to know. Shield battery is a great project. Thanks for your work.

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