Mythkeep

A session is 25, 45 or 90 minutes. A ring of twelve seals closes as it runs; leave the app for more than ten seconds and a seal breaks. A finished session feeds a creature; an abandoned one leaves a mark on its record. Nothing you raise ever dies, and nothing you earn is taken back.

Halfway through, the whole shell went 8-bit. A pixel generator and an atlas pipeline followed, and most of the 48 × 4 sprites are derived rather than drawn — even the breathing.