Thrive

Thrive is an open-source evolution simulator that begins with the Last Universal Common Ancestor (LUCA) — a single-cell organism in the primordial soup of an alien planet — and follows your species across the stages of biological complexity. The first complete stage, Microbe Stage, has you piloting a single cell or a small colony through a watery environment, gathering resources, fending off other species, and reproducing to enter the editor where you can mutate your design.

The editor uses over 25 different organelle and structural parts, each grounded in real biological science. You place mitochondria to power respiration, chloroplasts to photosynthesize sunlight, pili to stab prey, flexible membranes to engulf other cells whole, or rigid cell walls for defense. The combinatorial space is genuinely deep, and the population dynamics simulation continuously evolves the other species in the world alongside yours — adapting to predate you better, escape your hunting style, or compete more efficiently for shared resources.

The world itself is dynamic. Hydrothermal vents in the deep sea, ice shelves on the surface, and intermediate biomes all support different chemistry and different strategies — and these environments themselves change over geological time, with asteroid impacts or ice ages occasionally upending entire ecosystems. Endosymbiosis lets you absorb other species as permanent parts of yourself. Photosynthesis, chemosynthesis from hydrogen sulfide, iron-burning chemolithotrophy, or simply eating everyone else are all viable strategies. Multicellular Stage extends the game into multi-cell colony management, with later stages currently included as prototypes pointing at where the project intends to grow. The whole thing runs on Godot Engine in C# and welcomes contributors.