The first impression I had after looking at Darkout’s screenshots: it’s beautiful! Actually playing the game proved that screenshots didn’t lie: Darkout is by far the most beautiful game in 2D sandbox exploration/building genre, and while I believe that graphics isn’t that important, great graphics like this certainly adds to enjoyment.
Graphics aside, Darkout has decent crafting and building system; there is a fair (but by no means spectacular) selection of decorative items to craft, and some interesting features, like research system or necessity to connect most advanced work stations to your base’s power grid.
Overall, Darkout has interesting early to mid-game. Finding resources and progressing can be quite challenging, as even early enemies can be deadly when you are poorly equipped, and environment itself can present hazards like long falls or deadly tar pits. As you progress through the game, however, the challenge diminishes, not increases: while you start encountering stronger enemies, their strength increase doesn’t match your stronger weapons and armor, and eventually even hardest areas become a walk in a park with late-tier sword and armor.
Aside from drastically diminishing challenge, as you keep playing you will eventually find Darkout rather lacking in variety: there are only 3 surface biomes, not counting very small and very empty coastline biome, and flying islands biome that looks the same as surface jungle biome (other than being composed of flying islands, naturally). There are several different underground layers, but only major difference between them is the music and what kinds of resources you can find there. Also, there is only one boss, and it can only be fought after a rather long questline.
In the end, despite its flaws, Darkout is a good enough game, and if you are a fan of 2D sandbox exploration/building genre, Darkout will likely give you many hours of enjoyment.