×First through Fifth Level: This is KDD. The challenges are easy and fun for rooms I've done a few dozen times.
Sixth Level: This is indeed repetitive, but the secret room was pretty memorable, so I'll give it that.
Seventh Level: Snakes, more challenges and the Master Intellect room, pretty fun.
Eighth Level: Tar is fun, but Gel is my favourite.
Ninth Level: It's like herding cats. Fun, but kinda annoying.
Tenth Level: Spiders! Even though they're hidden roaches, they still were a good change of pace from all the roach measuring on the Ninth Level, plus the JtRH secret area.
Eleventh Level: No more Tar mazes. Alpha Blending became permanent after this floor.
Twelfth Level: I'm pretty sure some of these serpents are longer than the one in the Master Intellect room.
Thirteenth Level: It was more fun trying to find 2N2W than it was the roach and exit.
Fourteenth Level: Unlimited Undo helped me learn unbrained goblin movement, one of the best skills I got from KDD.
Fifteenth Level: Nothing can save you from the trapdoor puzzles, not even H&S. Never Again.
Sixteenth Level: Fun, but even after taking a break after the Fifteenth, I still had reservations toward the rest of KDD.
Seventeenth Level: I expected nightmarish efficiency puzzles, hoarde management but instead had fun with the Tar.
Eighteenth Level: It felt like filler, unfortunately not too memorable, other than the diagonal goblin rooms.
Nineteenth Level: Lots of door-clicking and dancing around the ememies. It was actually pretty fun.
Twentieth Level: Intro to Brains; Gunthro did it better.
Twenty-First Level: Practial Application of Brains; Unique puzzles thrown in with one of the best secret rooms in KDD.
Twenty-Second Level: Have I mentioned how much I hate mimics?
Twenty-Third Level: How can I use anything but goblins to complete this room?
Twenty-Forth Level: If I ever have to do 1S1W & 1S2W ever again, I'm gonna go cyberpsycho. The rest of Neatherville had some interesting puzzles, but the sheer awful-ness of the two interconnected tar rooms nearly prevented me from completing KDD.
Twenty-Fifth Level: Apart from 2S, this is one of the best final levels in a video game. The Neather can be outwitted logically in all but the aforementioned room; yet my biggest disappointment is not being able to spare him, because it is indeed possible to get to the final roach without slaying him.
Post-Mastery thoughts: KDD was really janky. Many rooms, especially when held up against TCB and later, feel kinda broken or just tedius. I felt this was especially true after the Twenty-First Level, where the mimic rooms felt like the same song-and-dance as each other, just with slight changes. Cheap tricks were abound in KDD: like the 350 room (cool concept, poor execution), invisible tarstuff mazes, and even plausibly broken scripting.
The secrets often became the highlight of a particular floor, and the post 5.0 challenges sometimes gave away the 'easy' answer to a room—I often took the challenges and tried most of them at least once before giving up and going another way. This honestly alleviated the tedium, and likely reduced my chances of going to H&S, by showing that there was more than one way to solve a room, something these early rooms weren't good at.
Yet as I walked down the stairs to the Twenty-Sixth level, I felt a sense of accomplishment, and when it said I had 100% of secrets, I skipped the credits and went up to the Post-Mastery level, completing each room once more before putting down KDD; I finally 100%ed a DROD game, having just conquered TCB the day prior. But now that I've done this, I honestly don't want to go back and do the challenges to 110% it.

×Part 1 – Into the Library: The first three levels of TCB aren't all that memorable for me. Yes, there's pressure plates and arrow rotators now, but Guide 186 was the most entertaining part. And it doesn't make any difference if you go to the Uncturage or Library first—Beethro still gets to see the Gourmet Diets section of the library before he'll consider asking about Butterflies.
Part 1½ – Under The Library: Briar is one of my favourite elements, and this level perfectly introduces it. Each time I redo this level, I have just as much fun each time.
Part 2 – Dugandy: After the fegundo level with the Negotiatior, the next three levels were excellent introes to 3.0 features and monsters, with my favourite being Midway Outpost with all the adders.
Once I made it into Dugandy, I somehow managed not to kill a single guard, which suprisingly made the throne room escape easier, and prompted Gossipper convos I'd never heard before.
Then came River Dugan, the first Problem Level I had back 10 years ago, and I wiped it clean wondering how I had such difficulty with it (especially 4S3E).
After that was the Holding Vats and the fun Tarstuff switcher tokens and somewhat redundant vision tokens. Alpha Blending was on permanently at this point.
Part 3 – Return to the City: There's a lot of story in The City, and after vanquishing the slayers without the decoy potion somehow (I'm still trying to do the other version in the mastery level), I found the taunting Mastery Wall before quickly clearing the Archival Catacombs and Torture Chambers. Then it was the Oremite level where unlimited undo again was my best friend, and then to Estengard.
Part 4 – Things get harder: I love Gel. It's my favourite tarstuff, and a level like Rasarus Archipelago is perfect to intro the viscous gel. I finished that up, then entered the second of my former Problem Levels—Pirate Hideout (mostly 4N1W).
And just like before, it wasn't as hard as I'd once made it out to be. Pirate Hideout was complete, Entengard had been warned, and off we went to the Asking Chamber.
Part 5 – The Ending I Finally Experienced: It was at last back to the Infohut, and down to the level I'd been stuck on for years—Forgotten Ruins. Aumtlich are nasty, but after so much spent on this, I persevered to clear the level and enter the Frozen Depths; I had a great time with the Gel, but the Stalwart section made me groan more often than I liked.
Then, after what felt like a brief intermission with the Rock Giants, came one of my new favourite levels: Abyssian Fortress.
The tarstuff puzzles felt original, and though most of them required efficiency in excess, it was rewarding, although I think the final two levels made me enjoy Abyssian Fortress more.
Why? Upper Lowest and Lowest Proper had too many rooms that felt like cheap tricks. Yes, builders can be used effectively, but many of the rooms felt like throwing dice and hoping the builders act like you want (UL: 1N, 1S, 1S1W, 1E, & 2E; LP: 1W & 1N come to mind as the worst).
And after all that, I finally walked down the stairs and saw the miracle that was Lowest Point. Wow. I couldn't belive I'd made it this far all on my own. I revelled in the glory, then committed to mastering the hold.
Post-Mastery Thoughts (as of writing only 7 of the 12 Undercity rooms were complete): It felt easier than KDD (I know it wasn't, but the puzzles were more fun), and honestly more fulfilling. Each room had resolution, and as the story went on, I caught more details that kept me going until Lowest Point. The learning curve felt pretty balanced, too, as even what I felt like filler levels were just as important as everything else, especially when it came to sharpening your skills and learing strategy for what inevitably came next.
Nothing in TCB really felt out of place or broken, and of course it was fun to try and complete the 5.0 challenges, or at least as many as I could. Unlike KDD, I feel like I want to complete the challenges too. I had fun, and it wasn't just in the completion and mastery—it really was all about the puzzles.