The building mechanic with the different rooms, is interesting, you need to manage space and position the rooms to minimize the damage and spread when you have an invasion, or a fire. You build your shelter with different rooms, try to maintain a good balance of resources and energy, assign survivors to the different rooms depending on their SPECIAL stats and develop your survivors doing missions, work or training. Luckily for us, on PC you can install mods to disable all the annoying slowdown mechanics and enjoy the core game, which is surprisingly fun. Like all free to play mobile games, gameplay is pretty easy and fun at the start, and becomes slow and boring after a while, forcing you to spend a TON of time, or money to progress. Sound effects and music are nice, nothing special. It's fun to watch the characters doing various activities in the vault. Really nice graphics and animations, the mix of 2D characters with 3D environments is great.

Fun (if modded) free to play mobile game.

How to install mods for fallout shelter