Walkthrough
SOMA does not feature any loading screens throughout the entire game, but the name of the levels will appear in the Load Game option at the Main Menu. For that reason, this walkthrough is split up into each level's name.
You cannot choose a difficulty level in SOMA, and only the main story will be told by the primary characters in the game. A lot more back story can be discovered by exploring every inch of each area and interacting with every note, picture, computer, black box, and intercom you can find. These are all completely optional, as there aren't any achievements or trophies tied to collecting them.
If you're new to SOMA, you may want to view the Tips and Tricks section for some advice before playing the game. There are a few control hints that appear on screen during the game, but most of SOMA has a learn as you go curve.