A dish of single cells that eat, divide and mutate. Nobody designs them. Whatever survives on this plate is whatever the plate rewards.
Tap a cell to read its genome. Tap bare agar to drop nutrients.
Each cell burns energy every minute. Bigger bodies, faster swimming and wider sensing all cost more. A nutrient pellet is worth the same to every cell, so large cells need more meals before they can divide.
A cell that fills three quarters of its energy store splits in two. The daughter inherits speed, size, sensing, carnivory and stain colour, each nudged by a small random mutation. Each founder line starts with its own stain, so you can watch one family take over the plate.
Every founder is a grazer. Carnivory is one more gene, and once in a while a division flips it hard. Cells above 50% carnivory that are a fifth larger than a neighbour can lunge at it and eat it. Prey swim away from anything that could.