Evolve
Pick a stage, an alignment and a type, then set what has been pulling on the chao and how far it has got.
What you are looking at
An adult chao's shape is pulled by four influences: swim, fly, run and power. Animals push one up gently. A chaos drive pushes one up sharply and drains whichever rival is highest, so sculpting is a transfer rather than a deposit.
Two independent things decide the result.Direction is which stats are pulling and in what proportion, set by the four sliders. Development is how far the transformation has got, set by the age slider. Zero every influence and run the age slider up for the other thing a second evolution can be: an adult that simply matured.
Two at once is not half of each
Push two sliders to 100% and both express in full rather than splitting one form's worth between them. Each morph target runs from the chao's young shape to its own mature destination, so the two mature forms combine and the maturation they both carry is counted once.
Two tracks at 50% each is the half-and-half case, and it looks different. Both are reachable in play.
Children
Children have no second evolution to steer, so the influence sliders are off for them. They have a trait instead: the strict leader of what you have given the chao so far, which the silhouette starts telegraphing hours before the cocoon. Alignment and type both reshape a child, since the child model carries all fifteen combinations of the three alignment arms and the five stat shapes, and the age slider is that trait fading in.
The 60% floor
In ordinary play a chao is held to at least 60% of its committed sub-type. If training would leave it weaker than that, the sub-type is lifted and the others are squeezed down, which stops a chao drifting into a shapeless mix of all four.
Lock a track, or feed a drive that moves anything, and the floor is gone for good. From then on the blend is exactly your raw influence, which is what these sliders show.The second evolution guide covers the drives, the locks and the timing.
Why the model is behind a button
The chao are built on Sonic Adventure 2's own models, which stay in the game rather than on a web page. The picture you land on is pre-rendered, and the interactive mode fetches a single model pack only when you ask for it. The gallery holds only original models for the same reason.
That mode is not an imitation of the game. It runs the game's own morph driver, subdivision, face genes, palettes and second-evolution colour, compiled into the page.