"Cannot play replay" version

[gth]

I stumbled across the replay feature and figured the 1hr 21m 56s speedrun would be cool to watch. When I went to replay the save file, however, the disabled play icon shows a tooltip: "Cannot play replay: it was created in version 1.1.88, but current version is 1.1.104"

Cue the disappointment. Can we either:
a) make replay work (almost) universally by making Factorio run "as" an older version, when necessary?
b) migrate replay/save files to the current version (maybe with an asterisk saying it may not be a perfect replica?)

PS: Is there any Steam functionality to downgrade to 1.188 myself, then update again later?

PPS: I watched the Youtube video but even at 0.5x I could barely keep up with their expertise-per-second.

[FuryoftheStars]

While I get and sympathize with the frustration, the only way for the game to "run as" another version is if it kept all of the data (game files) from that version to use (uses a lot of space). And just letting it run anyway, a single change, however minor, can very easily result in wildly different results. It is, unfortunately, the nature of the beast.

The only true way that I can think of for them to avoid this would be a true, full-on recording (a lot more space required) vs simply recording player actions.

PS: Is there any Steam functionality to downgrade to 1.188 myself, then update again later?

Use the standalone version: https://factorio.com/download/archive/1.1.88

[gth]

Use the standalone version

Excellent; problem solved! Thanks!


(Some thoughts below, out of curiosity only...)

...the only way for the game to "run as" another version is if it kept all of the data (game files) from that version to use (uses a lot of space).

A delta-based approach would be smaller in terms of disk space, but a lot of dev work for such an edge case as this.

...letting it run anyway, a single change, however minor, can very easily result in wildly different results

I don't know what's stored in the replay file, but yes understandable that code changes mean a broken replay.

The only true way that I can think of for them to avoid this would be a true, full-on recording (a lot more space required) vs simply recording player actions.

Could there be a middle ground? At the high end, a "full recording" could be a video-compression based recording of the map changes and more, while at the low end, from what you mentioned earlier could be almost as little as map seed + player inputs. Perhaps recording sufficient inputs AND game-code responses might eventually reach the point where the replay feature becomes version-independent? I'm guessing only a dev would know + would require a rather beefy machine / fast disk, performance warning, etc. Would assume prior game assets were still accessible some how, too. Again, I'm sure the authors would say far too much dev work for such an edge case.

Looking forward to 2.0.

[FuryoftheStars]

I don't know what's stored in the replay file, but yes understandable that code changes mean a broken replay.

Afaik, the map exchange string, mods used, and player inputs. So a replay is nothing more than another, fully simulated game session using the same map & mods (if any), where the "player" is essentially nothing more than a bot that's been preprogrammed by the player's recorded session. This means that even things as simple as recipe ingredient changes, crafting speed, or even the character's movement speed can affect the results.

[boskid]

Cue the disappointment. Can we either:
a) make replay work (almost) universally by making Factorio run "as" an older version, when necessary?
b) migrate replay/save files to the current version (maybe with an asterisk saying it may not be a perfect replica?)

a/ No.
b/ Absolutely No.

[gth]

Just to round out the discussion: running the old version (unpacked the zip, so it didn't impact the current Steam version) replayed the aforementioned save file just fine. No need for any dev work. Thanks again.