"Heist at Hilbert's Highrise Hotel" is somewhat of a departure from regular Thief-fare, to the point that I felt weird playing it after playing some recent FMs and the Anniversary Contest-entries. Garrett is tasked by a fellow Keeper to retrieve an odd stone that's currently on exhibit at Hilbert's Highrise Hotel, a swanky hotel with more security than you swing a Mechanist at, so it's close to being a manor heist. That doesn't describe accurately how it plays, though.
The primary aspect of this FM is the architecture and level design, with the puzzles and story coming in second and seemingly everything else being an afterthought. What that really boils down to is that this is the Mother of all Key Hunts, with lots of Running Back and Forth involved. There are some token guards around the place, but with the exception of Benny they're not even trying to be efficient or a serious hindrance. So most of the time playing this will involve Figuring Out Things. Like how to get anywhere, for starters. Here's a pro-tip: You get a note addressed to Kevel at the start, read it carefully. The start of the FM is needlessly restrictive in where one can travel, but once you get past the penthouse-gate things improve as the place opens up. I spent way too much time just looking at the scenery and trying to plot routes to hard-to-reach places, something that is a consistent throughout. Seeing a bunch of windows and finding that one of them is accessible became too common an occurance.
The two main themes of this FM are mathematicians and the concept of infinity, tied together in a neat story that entertains and kept me going, at least. Both get referenced throughout, either via clever name-droppings and motifs, or by flat-out trolling of the player.
The architecture is both the greatest feature and the greatest point of critique. Hilbert's Hotel is beautiful and fun to explore (the spiral staircase knocked me for a loop) but it's also full of twisty passages and barren sections. Combine that with all the Running Around needed for the puzzles and keeping an eye out for those bottlenecks that stop further progress, and I can understand some players getting overly frustrated playing this. There's a key ring included to make the Key Hunt-aspect a little less painful, but it also messes up because it doesn't inform what key was just picked up. So instead of having an inventory full of keys and having to test every locked door with each one, players will end up testing every locked door with one key. Not much of a difference sadly. As for the puzzles they're generally very clever and thought-out, either employing established mechanics or using the level design, but the color-coded combination safe was Too Much. The safe is found somewhat early, but the solution comes much later, to the point that people may have forgotten about the safe due to all the other stuff going on. It's also possible to screw this one up, as part of the solution (though not an essential part?) are a couple of loot items. I had to consult the TTLG-forums to find the answer to this one, and I was not impressed.
Technically HHHH is also a little rough on some edges. The soundscapes in the mission are not well done (I could hear a guard snoring through two walls in one place, while in another I couldn't hear a guard patrolling in a room through an open doorway) and the music used for the exterior and the penthouse-part of the museum are playing too loudly, I had trouble hearing the game itself over them, and they also feel out of place. I would go into the files and manually edit them myself (Are they part of the Star Wars-soundtrack?) but the thing is... overall I don't think I'll be playing this one again. Maybe it's because I somehow found all but 50 of the loot and all the secrets, but maybe because HHHH just burned me out. Lots of little things working together to annoy me. It was fun while it lasted and I'm glad that I saw it through, but the novelty is sadly only good for one playthrough.
One final note: The mission ends on a massive cliffhanger and I for one would love to see a sequel to this, despite everything.
Rating: 7-7.5/10