Absolutely love it. Love how unique and thematic the mechanics are. The pacing is great. The discovery feels natural and rewarding, not just because you get better numbers, but because there are new mechanics to explore that all feel worthwhile.
A "clear map" button would be a huge quality of life improvement. Right click to place field without having to go back to the menu would be nice. Click and drag to place multiple tiles would be nice as well. I want to experiment with more layouts, but it's getting very click intensive.
A compendium of your discovered tiles would be good, in case you forget how to lay something out, or are slightly unclear on what the rule is, and so you'd know if you've found everything. Having to try every tile combination to be sure isn't ideal.
It might be nice to use a 3x3 kernel for adjacency bonuses. It's kind of a feel bad to be able to make all these cities that give 50% adjacency bonus, but they mostly grant the bonus to the tiles that you need in order to make them in the first place, which often don't score much (or anything)
It seems like every tile is has a build-around that is somewhat viable in the mid/late game except for forests. You throw a few of them into your other layouts, but it's marginal benefit. Maybe forests (or one of the forest villages) could get a bonus for every other forest in the clump, instead of just the adjacent ones--similar to the way ports work. Given how aggressively tile costs scale, this doesn't seem like it would get out of hand in the early game, and in the late game it would give you something to do with the only tile you can often afford. Maybe that's too complicated to introduce so early in the game though.
I'm not sure I love the cost scaling in general. It means that specializing in one type of tile will almost always be worse than building a few of everything (at least until you run out of land, which I'm not that close to being able to do yet). Ideally you'd want the option to do either for a more creative experience.
I'm missing one tile still, and maybe I don't know about some combinations, so it could be the some of these (minor) complaints are dealt with anyway.
5/5 so far, and it still feels like there is a ton of design space to explore!