type Message = {
  from: "me" | "them";        // me = sent (right/blue), them = received (left/gray)
  text: string;
  typingMs?: number;          // show typing indicator this long before the bubble (received only)
  delayMs?: number;           // read-gap AFTER the previous bubble, before this one
  status?: "delivered" | "read";  // receipt under the last sent bubble
  reaction?: "❤️" | "👍" | "😂" | "‼️" | "❓"; // tapback, lands ~400ms after the bubble
};

const thread: Message[] = [
  { from: "them", text: "wait you're WHERE right now", typingMs: 900 },
  { from: "me",   text: "outside your house 🙂", delayMs: 600, status: "read" },
  { from: "them", text: "...", typingMs: 1400, reaction: "❓" },
];

const BUBBLE: React.CSSProperties = {
  maxWidth: "74%",                // never full-width — leaves the "this is a phone" gutter
  padding: "14px 18px",
  borderRadius: 22,
  fontSize: 34,                   // ~iMessage proportions at 1080px wide
  lineHeight: 1.25,
  wordBreak: "break-word",
};
const SENT: React.CSSProperties = {
  ...BUBBLE, alignSelf: "flex-end", background: "#0A84FF", color: "#fff",      // iMessage blue
};
const RECEIVED: React.CSSProperties = {
  ...BUBBLE, alignSelf: "flex-start", background: "#3B3B3D", color: "#fff",    // dark-mode gray
};

import { useCurrentFrame, useVideoConfig, spring, interpolate, Sequence } from "remotion";

const Bubble: React.FC<{ enterFrame: number; sent: boolean; children: React.ReactNode }> =
({ enterFrame, sent, children }) => {
  const frame = useCurrentFrame();
  const { fps } = useVideoConfig();
  const p = spring({ frame: frame - enterFrame, fps, config: { damping: 14, mass: 0.7 } });
  return (
    <div style={{
      alignSelf: sent ? "flex-end" : "flex-start",
      transform: `translateY(${interpolate(p, [0, 1], [24, 0])}px) scale(${interpolate(p, [0, 1], [0.85, 1])})`,
      opacity: interpolate(p, [0, 1], [0, 1]),
      transformOrigin: sent ? "bottom right" : "bottom left",
    }}>{children}</div>
  );
};

// three-dot typing indicator — dots breathe on a sine, frame-driven (no CSS animation timers)
const Typing: React.FC = () => {
  const frame = useCurrentFrame();
  const dot = (i: number) => 0.4 + 0.6 * (0.5 + 0.5 * Math.sin((frame / 8) - i * 0.9));
  return (
    <div style={{ ...RECEIVED, display: "flex", gap: 8, padding: "18px 20px" }}>
      {[0, 1, 2].map(i => (
        <span key={i} style={{ width: 12, height: 12, borderRadius: 6, background: "#aaa", opacity: dot(i) }} />
      ))}
    </div>
  );
};

const f = (ms: number) => Math.round((ms / 1000) * fps);
let cursor = 0;
const timeline = thread.map((m) => {
  cursor += m.delayMs ?? 500;                          // read-gap before this message
  const typingLen = m.from === "them" ? (m.typingMs ?? 800) : 0;
  const typingStart = cursor;
  cursor += typingLen;                                 // typing plays during the gap
  const enterMs = cursor;                              // bubble pops the instant typing ends
  cursor += 250;                                       // settle before the next read-gap
  return { ...m, typingStartMs: typingStart, typingLenMs: typingLen, enterMs };
});
const durationMs = cursor + 1000;                      // tail pad so the last bubble is readable

// targetY = total height of messages above the viewport floor, recomputed as bubbles enter
const scroll = spring({ frame: frame - lastEnterFrame, fps, config: { damping: 200 } });
const y = prevY + (targetY - prevY) * scroll;   // ease from old offset to new
return <div style={{ transform: `translateY(${-y}px)` }}>{/* bubbles */}</div>;

import { Audio, staticFile, Sequence } from "remotion";
{timeline.map((m, i) => (
  <Sequence key={i} from={f(m.enterMs)}>
    <Audio src={staticFile(m.from === "me" ? "send.mp3" : "receive.mp3")} />
  </Sequence>
))}

# Stills WITH SHIPPED PROPS (the real thread) at: a typing beat / a mid pop / the last bubble
npx remotion still TextThread out/f-typing.png --frame=24  --props='{"threadSrc":"thread.json"}'
npx remotion still TextThread out/f-mid.png    --frame=90  --props='{"threadSrc":"thread.json"}'
npx remotion still TextThread out/f-end.png    --frame=N   --props='{"threadSrc":"thread.json"}'  # N = durationInFrames-1

# Inspect each PNG:
#  - frame 24 shows the three-dot typing indicator on the LEFT (received), no real bubble yet
#  - at the mid frame the just-landed bubble is on the correct side/color with its tail; receipt/reaction placed right
#  - thread is auto-scrolled so the newest bubble sits in the lower third, NOT hidden under the compose bar
#  - app chrome consistent (status bar, header) and inside the 9:16 safe band; nothing under the top notch

npx remotion render TextThread out/thread.mp4 --props='{"threadSrc":"thread.json"}'   # encode once stills are right
npx remotion render TextThread out/demo.gif --codec=gif                               # README proof clip