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Cataclysm-DDA
Cataclysm - Dark Days Ahead. A turn-based survival game set in a post-apocalyptic world.
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InfluxDB
Power Real-Time Data Analytics at Scale. Get real-time insights from all types of time series data with InfluxDB. Ingest, query, and analyze billions of data points in real-time with unbounded cardinality.
Well you're out of luck on the spend money part but since you did mention Dwarf Fortress I'm assuming you're OK with obscure free games. You could give Cataclysm: Dark Days Ahead a try. It's about as deep a sandbox as they come and it's no easy task to get into.
NOTE:
The number of mentions on this list indicates mentions on common posts plus user suggested alternatives.
Hence, a higher number means a more popular project.