The built-in eases cover the usual shapes, but a game often wants its own: a coin that bounces twice, a door that overshoots and settles. A new asset type holds such a curve, and keys and the Lerp node can pick it instead of a built-in ease. - New asset type "curve": points like in Vector art, x is t and y is the value. A new curve is the straight line from (0, 0) to (1, 1). - One pure evaluation in src/core/model/curve.ts serves the timeline preview, the running game and the Lerp node. - The curve always has one value per t. The end points stay at t 0 and 1, points cannot pass each other, and a handle that reaches past its neighbour is shortened along its direction. Loading a hand-edited file applies the same rules. - Curve tab: click on the line to insert a point that keeps the shape, click on free space to put one there, drag points and handles, double-click or Delete removes, Alt-click toggles round and sharp. Every step is one undo step. - Presets: all 30 built-in eases plus Linear, fitted with adaptive subdivision. Each stays within 0.4 % of the built-in ease. - Preview: a dot runs along the curve once a second, a second dot shows only the value. The Preview button stops it. - Animation keys get "Curve" under Easing with a curve picker. Lerp gets "Curve" under Ease, and its result may overshoot b. - A missing or unpicked curve runs linear. The inspector says so, the node shows it as a problem, and deleting a used curve warns with the number of keys and Lerp nodes. Tests: - ./check.sh: 180 files, 2612 tests, CHECK EXIT 0 - GM_STEPS=1-6,25,53: ALL PASSED, 309 checks - New e2e module 53 with 13 checks, all with the real mouse. Expected values come from its own Bezier evaluation. - Counter-checks bite: without Bezier evaluation 4 unit tests fail, without handle clamping 2. In the browser, a key that cannot find its curve, a click that sets no point and a handle drag that moves the point all turn checks red. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>