Screen Transition Part 2

Basics: stage 470×222px, background #13131C, all coordinates in px from the stage's top-left, everything clipped to the stage (its two top corners are rounded with radius 40px; the bottom corners are square). App window (a wide made-up app that nearly fills the stage): rr(20, 8, 430, 206, 18) filled #171626 with a shadow rgba(0,0,0,0.55), blur 16, offset y 4. Everything of the app is drawn clipped to that rounded rect, in window-local coordinates (local (0, 0) = stage (20, 8); local size 430×206). After the app, stroke the same rounded rect with a 1.5px rgba(255,255,255,0.16) border (a thin bezel). Fingers are drawn last, in stage coordinates, not clipped to the window.

Forward is a tap (the page slides in from the right). To go back, a finger presses the page's left edge and drags it right; the list underneath follows with parallax, and on release the page flies off. 
- Page position sx (0 = page fully shown, 1 = page off to the right): fwd: sx = 1 − easeIO(k). Back: d = seg(u, 2.55, 3.0)²; sx = 0.5·d while u < 3.0 (the drag speeds up), else lerp(0.5, 1, ease(seg(u, 3.0, 3.68))) (the fly-off; at the release both move at 2.22 sx per second, so the speed is continuous).
- If sx > 0: screen A translated by (−129·(1 − sx), 0), then dim(0.4·(1 − sx)).
- If sx < 1: translated by (430·sx, 0): fillRect(0, 0, 430, 206) #171626 with a shadow rgba(0,0,0,0.6) blur 16, offset 0; screen B with its back button at scale 1 (in this type the back button is never pressed: backPress = 1); then, only when going back, an edge glow: fillRect(0, 0, 14, 206) with a horizontal gradient from rgba(56,198,255,0.75) at x 0 to rgba(56,198,255,0) at x 14, at opacity held = 1 for 2.5 ≤ u < 3.0, 1 − seg(u, 3.0, 3.15) after, 0 before (it lights when the finger lands).
- Fingers: only the card tap (no back-arrow tap). Plus holdMark(min(32 + 430·sx, 425), 111, T0 = 2.5, T1 = 3.0) when going back (x is capped at 425 so the fading mark is never cut by the stage's right edge) (stage coordinates; in the forward half it is hidden anyway): it presses 12px inside the page's left edge, drags 215px right with the page, and after the lift it keeps riding the page edge to the right while it fades, so it never rests over a card like a tap.
- Draw order: A, dim, page shadow, B, edge glow, card tap, hold finger.