Outer Wilds - dozens of hours into it but still nowhere near solving it (I think). This game's brilliant: a blinding flash of light rapidly engulfs the galaxy and kills you 22 minutes into each "life". I have no idea what causes this light, no idea if I can stop it.
But I've visited the planets of my solar system (those I can land on that is) and had involved quests on each, upon completion of which information is added to what quickly becomes a sprawling Mission/Sub-mission red-string board:
The graphics are nothing spectacular, but they make the game. The space-flight is arcade-like, but it's secondary to the story line.
Worth putting on your wish lists and grabbing when on sale next.