This review was published when the game was in v1.145 (most likely the final update, but mentioning just in case).
Theme: Milestones. Executed very well, with 145 milestones (even The Tree of Life only has 100 in a single layer) and additional ones.
Gameplay and core mechanics: The first layer has milestones you reset for once you have enough points. The first produces points, the second is a static boost, the third boosts the first based on your points, and then the later ones provide things like new layers, upgrades, challenges, automation, and boosts. Most lower layers don't have milestones, but instead provide their own resources alongside new upgrades and buyables (luckily, milestones are never reset).
Balancing and difficulty: Fluctuating. The early game is fast and you generally don't have much to choose, with the only option being resetting again in case you don't measure up enough to continue. Some parts early on may feel like there's a lot of resetting, but the white node glow generally helps you know when to do it and the milestones are given before things get too tedious. Once you get into Atomic-prestige, you gain access to challenges that you have to figure out which one you're strong enough for or whether you should aim for an upgrade. Once you get to transcension, the game offers several different upgrades to choose from and eventually grants effects that improve gains/lower the point softcap/lower the milestone cost scaling and new challenges open up, giving you a lot of freedom regarding whether you want to grind TP or do AP/T challenges, with the former allowing for fractional completions and the latter gaining a new currency to not make them feel like a waste. By the end, the game gets rather slow, but very lenient (upgrades still make the most major difference, but you have a decent amount of freedom in regards to whether you want to play active or idle).
Content on offer: Average length, the game should take half a day to a day to complete. There's a little more to do in the postgame to get the last Hyper-prestige upgrade (TP is hardcapped at 1e16 and the balancing won't let you get to 146 milestones, so don't try it — I did). 12 layers that range from almost empty to large.
Polish and miscellaneous additions: No interesting editions, but no glitches or typos.
I think this is probably the best "gimmick tree" that you can play. While I would surely welcome more content, what's already present is quite a satisfying experience that grows more non-linear as you play while still having a clear linear goal.
Maybe not a developmental milestone, but still super (v1.145)
This review was published when the game was in v1.145 (most likely the final update, but mentioning just in case).
I think this is probably the best "gimmick tree" that you can play. While I would surely welcome more content, what's already present is quite a satisfying experience that grows more non-linear as you play while still having a clear linear goal.
Overall rank: A (Awesome)