This video goes over how we searched for a good gameplay loop in SOMA while still making sure the themes got through to the player.
Other videos mentioned:
Core Loops:
https://youtu.be/M7u-hi_lwoc
Design Attractors:
https://youtu.be/mCkPgATsjfI
When Optimizing Fun Fails:
https://youtu.be/bc3_FYrpPWM
Game was perfect sci-fi horror.