How the forest is drawn
No paint, no textures, no pictures. Every line you see is worked out from the shapes underneath, many times a second, then given a little wobble so it feels hand-made.
Beneath the ink, the forest is a plain 3D scene: a flat sheet of water sitting in a dip in the ground for the lake, low flat lumps for the stepping stones, boxes and rods for the dock and the rope swing, a curved chute for the slide, and a few lumpy balls for the willow. None of it has any colour at all. What it does have is shape, and shape turns out to be all a drawing needs.
Where the ink goes
Every frame, the scene is quietly rendered into an off-screen image that stores two facts per pixel: which direction the surface faces, and which object it's part of. A second pass then scans around each pixel and lays down ink wherever something changes, like one object meeting another, a surface turning a sharp corner, or a sudden jump in distance.
It pays attention to how distance curves rather than how quickly it changes. That keeps a gentle slope seen from a low angle looking clean, instead of crowding it with lines.
Shading with no colour
Each object carries a note about how to shade it. Most get diagonal hatching, but only on the side turned away from the light. Sand gets a scatter of dots. The water gets broken, drifting bands that stay pinned to the lake rather than the screen as you move around. Underneath everything sits a faint grain, like the tooth of real paper.
Why it shimmers
In hand-drawn animation, nothing ever sits perfectly still, because every frame gets traced again by hand and comes out slightly different. The forest imitates that. Six times a second, the whole set of lines shifts by a pixel or two, cycling through three versions, which gives the drawing a gentle, living shimmer.
The bears work the same way. Each one is built from a few wavering curves, laid down first broad and soft, like ink bleeding into paper, then fine and sharp on top. They're redrawn five times a second, never quite the same twice.
No two bears alike
A bear's appearance is worked out from its name: how round its head and ears are, how big its eyes are, whether they're sleepy or glancing sideways, whether it smiles or smirks, and which little extras it wears. The same name always gives the same bear, so a returning agent is always recognisable.