WORLDS Builder is a free-to-play game that combines gameplay elements of Little Alchemy with the classic resource-gathering and production style of many other free-to-play world building games. Using base elements of earth, fire, water, life, sand, stone, and grass, you combine and recombine elements to create resources, which fuels your production buildings to create more products, many of which are then combined to make even more things. Products can then be sold in the marketplace for coin and experience points; the higher you level up, the more buildings you can build. It's a relatively simple game with fairly easy to understand rules. The game also receives support and new development from the developer, JoyBits, who has pushed out several updates over the past year to add new events and rewards.
Unfortunately, most of the major updates have only served to extend the grind, which is typically already an issue with free-to-play games. The first major update removed the ability to cross-train your villagers, locking them into a single profession (an update which also removed all bonuses players had previously earned). With training, villagers could level up and earn bonuses that increased production efficiency, and these bonuses would stack to provide much faster and more productive gameplay -- until another update capped the maximum that those bonuses could apply. One game mechanic, the expedition (where you could send villagers away for a time to earn bonus items), became crippled by another update, where all but the shortest expeditions now require an Explorer-type villager, which (due to the lack of cross-training from earlier) can only be found randomly at extremely low odds. And a later update removed the ability to train villagers by having them work; training now only comes from "books", which are found randomly (usually through expeditions) -- meaning it's entirely random whether or not you will be able to level up any specific villager. (To be somewhat fair, books are given fairly liberally; but it still takes longer than it used to, and now it's up to random chance.)
Perhaps most damning for achievement hunters is the fact that many of the achievements require making enormous quantities of various products, which due to the time constraints can take weeks or months of gameplay to even produce (also made more difficult by the limited warehouse space you are granted for storage; and the rarity with which those products are requested from the marketplace, making them harder to sell). The game also has one achievement, Home-for-All, that is only slightly better than unobtainable. The achievement requires building 12 houses (as of this writing), but normal gameplay and levelling up will only give you the opportunity to build 11. The twelfth house can only be obtained through weekend tournaments (where you have to create an obscene amount of items in a 3-day period) or the occasional "blitz" tournament (where you have to do the same, but in only 24 hours -- a feat that, according to their own leaderboard, is accomplished by fewer than 10 players, total). A house is very rarely offered as a prize, however (it was, at one point, OVER A YEAR between times a house appeared in the prize list), and even if you do earn enough points, you still have to unlock it with their premium currency.
If you have a desire to keep your total gamerscore ending in a 5 or 0, you'll definitely want to avoid this game. Many have odd scores, and the grand total doesn't add up to a round number, either.
WORLDS Builder is a fairly simple way to pass the time; but if you care about getting all of the achievements (especially if you care about your completion percentage) or having a score ending in a nice, round number, you're better off passing this one by.
[Edited 2021-05-03 to add further training restrictions, and to update the Home-for-All achievement issue]