Herbivore armour
Carnivore claws
Population
Tools Place Plant Place Herbivore Place Carnivore Place Meteor Place Wall
To use a tool, click on it and then click on the appropriate place on the world.
World Dynamics ${g}_{g}$ : Grass grow rate % of full per iteration
HerbivoreCarnivore
Metabolism
Eat efficiency ${e}_{b}$ : % ${e}_{r}$ : %
Metabolism rate (mass used per iteration) ${m}_{\mathrm{bc}}$ : ${m}_{\mathrm{rc}}$ :
Strength cost (mass used per iteration) ${m}_{\mathrm{ba}}$ : *armor ${m}_{\mathrm{ra}}$ : *claws
Maximum mass ${l}_{b}$ : ${l}_{r}$ :
Reproduction
Minimum size to reproduce ${r}_{\mathrm{bs}}$ : ${r}_{\mathrm{rs}}$ :
Mass lost by parent ${r}_{\mathrm{bc}}$ : ${r}_{\mathrm{rc}}$ :
Baby mass ${r}_{\mathrm{bb}}$ : ${r}_{\mathrm{rb}}$ :
Weapons mutation rate ${r}_{\mathrm{bm}}$ : ${r}_{\mathrm{rm}}$ :
Display Wall color
Warp (integer) iterations per display frame
FPS : ???
What is going on

There is grass growing (green), herbivores eating the grass (blue), and carnivores eating the predators (red). Each pixel can hold at most one animal, which will have a mass which will determine the intensity of the blue or red. Animals can have weapons (armour for herbivores, claws for carnivores). The probability of a carnivore successfully eating a herbivore is (1+claws-armour)*100%. Eating increases the mass of an animal; existing makes the mass reduce at a steady rate. Claws and armour both have a metabolic cost. When an animal gets sufficiently large, it reproduces, losing mass and creating a baby. The baby will have a slightly different amount of claws or armour. Grass grows at a constant rate and is completely eaten when a herbivore steps in.

Each animal can move at most one pixel per iteration. Note that is possible for a species to die out. More plants, herbivores and carnivores may be placed by act of god (you) using the tools above. You can also smite the ungodly if you wish with rocks from heaven.

Copyright 2016 Andrew Conway. All rights reserved. Credits to http://webglfundamentals.org for some infrastructure code. Picture's creators are in their metadata.