Lots of revision, although nearly all of that was polishing. Timewise, I think I finished the first draft of the game in mid-June of 2017. I can't remember for sure, but I think it may have been about 60,000-70,000 words in Inform 7 at that point. I sent it out to testers, some of whom (Brian Rushton, Andrew Schultz, and David White in particular) gave it a very thorough playthrough. I spent most of July and part of August responding to their suggestions and fixing bugs they found, as well as writing the hint system. The version I submitted to IFComp was nearly 120,000 words. I hadn't intended to write that much, but it just kept getting bigger as I kept fixing things, adding synonyms, etc. (The hint system is quite large, by the way - about 18,000 words. So it's roughly 15% of the entire game. For comparison, Junior Arithmancer is only about 20,000 words.)
Major changes resulting from testing... the biggest one I can think of has to do with the farmer. Originally you were supposed to acquire a black box that you could use to represent a problem algebraically. Then, when you met the farmer, he just described his problem to you instead of writing it down. You were supposed to activate the black box, which would represent his problem as an algebraic equation on a card of some kind. Then you use that card as normally in the published version of the game. The idea was to have the game emphasize that the process of modeling a real-world problem mathematically is a challenge separate from solving a math problem. But every one of my testers who got that far found the black box confusing, even after I tried multiple variations on the box. So I ended up scrapping it. Pennings the dog was a late addition, too, and he wasn't thoroughly tested. I expected players to find some bugs with him, but nobody has reported one so far.
Oh, yeah - another major change was a rejiggering of the locations on each level. Originally the Zork area was at the bottom level of the game, as I intended it to represent the development of computers as an outgrowth of mathematics in the 20th century. However, multiple reviewers complained that they were collecting a bunch of books that they didn't know what to do with. So I moved the Zork area up to a higher level and dropped the roller coaster and sequences-and-series machines areas down a level each to compensate.
The scene in the hotel was a late addition to the design, but it was probably before testing. Same with the 69,105 location.
I did make a few major changes to the game after IFComp 2017. A few of my testers had found the early room with the balance scales confusing - in the sense that they couldn't even figure out what they were supposed to be doing with it. But I had also had my then-nine-year-old son play through the early part of the game, and he (despite no algebra background) had figured the puzzle out. So I thought that if a nine-year-old could handle it, it was probably fine. Then, during IFComp, one of the most common criticisms I saw of the game was how confusing the balance scales puzzle was. I remembered that my son had been playing the game with me by his side, offering little nudges. So he hadn't figured the puzzle out independently, and I should have been listening to my testers all along! (General authoring principle: Listen to your testers!) So I rewrote part of the balance scales puzzle to make it more clear what's going on there.
Another big change had to do with the inventory limit. Again, I had the Infocom games and Curses as the IF templates in my head, so I thought it would be really cool to mimic Curses and have ABCA feature an inventory limit that could be overcome fairly early in the game with a carryall that the player can find. Well. I hadn't realized that many modern players despise inventory limits with the burning fury of 1000 suns, and I also hadn't fully appreciated that I had positioned the carryall in ABCA so that you could get at least a quarter or so of the way through the game without discovering it. IFComp enlightened me on both counts, and so for release 2 I made it much easier for the player to acquire the carryall. For what it's worth, three years later and much further into the modern IF scene I find myself agreeing that inventory limits aren't much fun and don't add a lot to most games. That still didn't stop me from enjoying - in a slightly subversive sort of way - creating a scoring system that incentivizes players to work with inventory limits in Sugarlawn. :)