Files
hyperframes/docs/catalog/blocks/split-flap-board.mdx
miga-heygenandMiguel Ángel 7b5fdb1ad2 fix(docs): emit catalog source accordion titles as plain strings (#4006)
The generated catalog pages rendered the "Source" accordion title as a
JSX expression, `<Accordion title={`name.html`}>`. Mintlify's search
indexer stringifies expression attribute nodes rather than evaluating
them, so every one of the 399 catalog pages surfaced its Source section
in search results as "[object Object]" (visible on the Scroll Feed page,
among others).

The template literal carried no escaping benefit: every title is a
single-segment `name.html` path, and a double-quoted JSX string handles
it directly. Introduce `mdxStringAttribute`, which emits a plain
`name="value"` attribute and escapes `& " < { }` as HTML character
references (MDX decodes references inside quoted attribute values, and
unlike JSON.stringify it does not rely on backslash escapes, which JSX
strings do not honour). Use it for both the Source accordion title and
the preview iframe title, and regenerate the catalog pages.

Regenerated with `npx tsx scripts/generate-catalog-pages.ts`; the only
change across the 399 pages is the one Accordion title line each.

Co-authored-by: Miguel Ángel <miguel.sierra@heygen.com>
2026-09-16 11:55:00 -04:00

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---
title: "Split-Flap Board"
description: "Solari-style departure board: every cell walks its drum forward through the intervening characters of a fixed alphabet until it lands on its target, so the text resolves as a mechanical cascade instead of a fade."
---
import { InstallCommand } from "/snippets/install-command.jsx";
import { VariablesExplorer } from "/snippets/variables-explorer.jsx";
## Install
<InstallCommand command="npx hyperframes add split-flap-board" item="split-flap-board" />
That writes one file: `compositions/split-flap-board.html`.
<VariablesExplorer
previewSrc="/public/catalog/blocks/split-flap-board.json"
compositionId="split-flap-board"
compositionSrc="compositions/split-flap-board.html"
variables={[{"id":"boardText","type":"string","label":"Board text","default":"NOW BOARDING","maxLength":24},{"id":"flapAlphabet","type":"string","label":"Flap alphabet (drum order)","default":" ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789.,'","maxLength":64},{"id":"flipDuration","type":"number","label":"Seconds per flap","default":0.09,"min":0.03,"max":1.2,"step":0.01,"unit":"s"},{"id":"cellStagger","type":"number","label":"Per-cell start stagger","default":0.05,"min":0,"max":0.5,"step":0.01,"unit":"s"},{"id":"cellCount","type":"number","label":"Cells on the board","default":12,"min":1,"max":24,"step":1}]}
>
```html split-flap-board.html
<!doctype html>
<html
lang="en"
data-composition-variables='[
{"id":"boardText","type":"string","label":"Board text","default":"NOW BOARDING","maxLength":24},
{"id":"flapAlphabet","type":"string","label":"Flap alphabet (drum order)","default":" ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789.,&#39;","maxLength":64},
{"id":"flipDuration","type":"number","label":"Seconds per flap","default":0.09,"min":0.03,"max":1.2,"step":0.01,"unit":"s"},
{"id":"cellStagger","type":"number","label":"Per-cell start stagger","default":0.05,"min":0,"max":0.5,"step":0.01,"unit":"s"},
{"id":"cellCount","type":"number","label":"Cells on the board","default":12,"min":1,"max":24,"step":1}
]'
>
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=1920, height=1080" />
<title>Split-Flap Board</title>
<script src="https://cdn.jsdelivr.net/npm/gsap@3.14.2/dist/gsap.min.js"></script>
<style>
*,
*::before,
*::after {
margin: 0;
padding: 0;
box-sizing: border-box;
}
html,
body {
width: 1920px;
height: 1080px;
overflow: hidden;
background: transparent;
}
</style>
</head>
<body>
<div
id="sf-root"
data-composition-id="split-flap-board"
data-start="0"
data-duration="3.5"
data-fps="30"
data-width="1920"
data-height="1080"
style="position: relative; width: 1920px; height: 1080px; overflow: hidden"
>
<style>
/* The root's own box lives in an inline style, not a rule: every
sub-composition rule is rewritten to
`[data-composition-id="split-flap-board"] <selector>` at render,
which can never match the root element itself. */
#sf-bg {
position: absolute;
inset: 0;
background:
radial-gradient(120% 90% at 50% 42%, #23242a 0%, #121317 62%, #0a0a0c 100%), #0a0a0c;
}
#sf-board {
position: absolute;
inset: 0;
display: flex;
align-items: center;
justify-content: center;
}
.sf-cell {
position: relative;
flex: 0 0 auto;
perspective: 900px;
border-radius: 9px;
background: #0c0c0e;
box-shadow:
0 18px 34px rgba(0, 0, 0, 0.55),
0 0 0 1px rgba(255, 255, 255, 0.05);
}
.sf-face {
position: absolute;
left: 0;
width: 100%;
height: 50%;
overflow: hidden;
background: linear-gradient(180deg, #26272c 0%, #1a1b1f 100%);
}
.sf-top,
.sf-leaf-a {
top: 0;
border-radius: 9px 9px 0 0;
}
.sf-bot,
.sf-leaf-b {
top: 50%;
border-radius: 0 0 9px 9px;
background: linear-gradient(180deg, #191a1e 0%, #232429 100%);
}
.sf-leaf-a {
transform-origin: 50% 100%;
z-index: 3;
backface-visibility: hidden;
}
.sf-leaf-b {
transform-origin: 50% 0%;
z-index: 3;
backface-visibility: hidden;
}
.sf-glyph {
position: absolute;
left: 0;
width: 100%;
display: block;
text-align: center;
font-family: ui-monospace, monospace;
font-weight: 700;
color: #f4efe2;
white-space: pre;
}
.sf-seam {
position: absolute;
left: 0;
top: 50%;
width: 100%;
height: 3px;
margin-top: -1.5px;
background: #050506;
z-index: 4;
}
</style>
<div id="sf-bg"></div>
<div id="sf-board" class="clip" data-start="0" data-duration="3.5" data-track-index="0"></div>
<script>
(function () {
window.__timelines = window.__timelines || {};
// ---------------------------------------------------------------
// Reference numbers (see report / research entry F#1)
//
// Alphabet: the 40-position drum from the scottbez1/splitflap
// project (Apache-2.0, README read) — blank, A-Z, 0-9, then `.,'`.
// Drum order is what makes the cascade read as a real board: a cell
// never jumps, it walks the drum forward through every intervening
// character, so letters resolve early and digits/punctuation late.
//
// Flip duration: the only published-ish figure is a DIY firmware
// proxy (28BYJ-48 stepper, ~83.59 steps/flap, a=500 steps/s^2 ->
// triangular profile -> ~1.16 s/flap). That is a hobby build, NOT a
// Solari spec, and real boards audibly flutter at tens of ms per
// flap. The default below sits in that observed band; the DIY proxy
// is still reachable at the top of the `flipDuration` range.
//
// Flap fall: constant angular acceleration through 180 degrees,
// theta(p) = 180 * p^2. The flap therefore hangs near the top and
// slaps down — no ease-out, because a falling leaf does not
// decelerate. The two CSS leaves are the two faces of that one flap
// (hand-off at theta = 90, i.e. p = 0.707).
// ---------------------------------------------------------------
var DEFAULT_ALPHABET = " ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789.,'";
var DEG = Math.PI / 180;
function num(value, min, max, fallback) {
var n = typeof value === "number" ? value : parseFloat(value);
if (!isFinite(n)) return fallback;
return Math.min(max, Math.max(min, n));
}
var vars =
window.__hyperframes && window.__hyperframes.getVariables
? window.__hyperframes.getVariables()
: {};
var alphabet = String(vars.flapAlphabet || DEFAULT_ALPHABET);
if (alphabet.length < 2) alphabet = DEFAULT_ALPHABET;
var N = alphabet.length;
var flipDur = num(vars.flipDuration, 0.03, 1.2, 0.09);
var stagger = num(vars.cellStagger, 0, 0.5, 0.05);
var cellCount = Math.round(num(vars.cellCount, 1, 24, 12));
var text = String(vars.boardText == null ? "NOW BOARDING" : vars.boardText)
.toUpperCase()
.slice(0, cellCount);
// Centre the string across the board; unused cells stay on the
// drum's first position (blank in the default alphabet).
var lead = Math.floor((cellCount - text.length) / 2);
var targets = [];
for (var i = 0; i < cellCount; i++) {
var ch =
i >= lead && i < lead + text.length ? text.charAt(i - lead) : alphabet.charAt(0);
var g = alphabet.indexOf(ch);
targets.push(g < 0 ? 0 : g);
}
// Geometry: fit `cellCount` cells across 1920 with a 120px margin.
var GAP = 10;
var cw = Math.min(130, Math.floor((1920 - 240 - (cellCount - 1) * GAP) / cellCount));
var chh = Math.round(cw * 1.45);
var board = document.getElementById("sf-board");
board.style.gap = GAP + "px";
function makeFace(cls, glyphTop) {
var face = document.createElement("div");
face.className = "sf-face " + cls;
var glyph = document.createElement("span");
glyph.className = "sf-glyph";
glyph.style.height = chh + "px";
glyph.style.lineHeight = chh + "px";
glyph.style.fontSize = Math.round(cw * 0.78) + "px";
glyph.style.top = glyphTop + "px";
face.appendChild(glyph);
return face;
}
var cells = [];
for (var c = 0; c < cellCount; c++) {
var cell = document.createElement("div");
cell.className = "sf-cell";
cell.id = "sf-cell-" + c;
cell.style.width = cw + "px";
cell.style.height = chh + "px";
// The mechanism IS clipped, stacked half-glyphs: each face holds a
// whole character and shows half of it, and the falling leaf sits
// on top of the face behind it. Declared intentional so the layout
// auditor reports real regressions instead of the design.
cell.setAttribute("data-layout-allow-overlap", "");
cell.setAttribute("data-layout-allow-occlusion", "");
cell.setAttribute("data-layout-allow-overflow", "");
var top = makeFace("sf-top", 0);
var bot = makeFace("sf-bot", -Math.round(chh / 2));
var leafA = makeFace("sf-leaf-a", 0);
var leafB = makeFace("sf-leaf-b", -Math.round(chh / 2));
var seam = document.createElement("div");
seam.className = "sf-seam";
cell.appendChild(top);
cell.appendChild(bot);
cell.appendChild(leafA);
cell.appendChild(leafB);
cell.appendChild(seam);
board.appendChild(cell);
cells.push({
// steps is unidirectional: the drum only ever spins forward,
// start position is always the drum's first flap (index 0).
steps: targets[c],
top: top.firstChild,
bot: bot.firstChild,
leafA: leafA,
leafB: leafB,
glyphA: leafA.firstChild,
glyphB: leafB.firstChild,
});
}
// A face that is not in use must be wiped, not merely hidden.
// Leaving a stale transform/filter/glyph on an opacity-0 leaf makes
// the DOM (and, via layer promotion, the rasterised pixels) depend
// on which frames were visited before this one — the exact failure
// seeking is supposed to be immune to.
function clearLeaf(leaf, glyph) {
leaf.style.opacity = "0";
leaf.style.transform = "";
leaf.style.filter = "";
glyph.textContent = "";
}
function showLeaf(leaf, glyph, char, angle, shade) {
glyph.textContent = char;
leaf.style.opacity = "1";
leaf.style.transform = "rotateX(" + angle.toFixed(2) + "deg)";
leaf.style.filter = "brightness(" + shade + ")";
}
// Pure function of absolute composition time. No accumulator, no
// dependence on the previous frame — seeking to any t reconstructs
// the whole board from t alone.
function paint(t) {
for (var i = 0; i < cells.length; i++) {
var cell = cells[i];
var tLocal = t - i * stagger;
var raw = tLocal <= 0 ? 0 : tLocal / flipDur;
var count = Math.floor(raw);
var p = raw - count;
if (count >= cell.steps) {
count = cell.steps;
p = 0;
}
var outgoing = alphabet.charAt(count % N);
var incoming = alphabet.charAt((count + 1) % N);
var flipping = count < cell.steps && p > 0;
if (!flipping) {
cell.top.textContent = outgoing;
cell.bot.textContent = outgoing;
clearLeaf(cell.leafA, cell.glyphA);
clearLeaf(cell.leafB, cell.glyphB);
continue;
}
// The new character is already seated behind the falling flap:
// its top half shows, its bottom half is still hidden by the
// outgoing flap lying in the lower slot.
cell.top.textContent = incoming;
cell.bot.textContent = outgoing;
var theta = 180 * p * p;
var shade = (1 - 0.5 * Math.sin(theta * DEG)).toFixed(3);
if (theta < 90) {
showLeaf(cell.leafA, cell.glyphA, outgoing, -theta, shade);
clearLeaf(cell.leafB, cell.glyphB);
} else {
clearLeaf(cell.leafA, cell.glyphA);
showLeaf(cell.leafB, cell.glyphB, incoming, 180 - theta, shade);
}
}
}
var duration = parseFloat(document.getElementById("sf-root").dataset.duration) || 8;
// GSAP suppresses events on seek(), so onUpdate callbacks never fire
// during a render. A property setter on the tweened driver always
// runs, because GSAP writes the value itself.
var driverTime = 0;
var driver = {};
Object.defineProperty(driver, "t", {
configurable: true,
get: function () {
return driverTime;
},
set: function (value) {
driverTime = value;
paint(value);
},
});
var tl = gsap.timeline({ paused: true });
tl.to(driver, { t: duration, duration: duration, ease: "none" }, 0);
paint(0);
window.__timelines["split-flap-board"] = tl;
})();
</script>
</div>
</body>
</html>
```
</VariablesExplorer>
## Add it to your video
It runs for 3.5 seconds at 1920×1080. Paste this into your composition:
```html index.html
<div
data-composition-id="split-flap-board"
data-composition-src="compositions/split-flap-board.html"
data-start="0"
data-duration="3.5"
data-track-index="1"
data-width="1920"
data-height="1080"
></div>
```
Move it in time with `data-start`. Put it on a different timeline row with
`data-track-index`. See [data attributes](/concepts/data-attributes) for the rest.
## Variables
Every one of these has a default, so the piece works untouched. Set the ones you
want to change on the element:
| Variable | Default | Accepts | What it does |
| --- | --- | --- | --- |
| `boardText` | `NOW BOARDING` | string | |
| `flapAlphabet` | ` ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789.,'` | string | |
| `flipDuration` | `0.09` | 0.03s to 1.2s, step 0.01s | |
| `cellStagger` | `0.05` | 0s to 0.5s, step 0.01s | |
| `cellCount` | `12` | 1 to 24, step 1 | |
Set them with `data-variable-values` on the element that mounts it. These are the
defaults, so this behaves exactly like the preview above until you change one:
```html wrap
<div
data-composition-id="split-flap-board"
data-composition-src="compositions/split-flap-board.html"
data-variable-values='{"boardText":"NOW BOARDING","flapAlphabet":" ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789.,'","flipDuration":0.09,"cellStagger":0.05,"cellCount":12}'
></div>
```
## Source
<Accordion title="split-flap-board.html">
```html
<!doctype html>
<html
lang="en"
data-composition-variables='[
{"id":"boardText","type":"string","label":"Board text","default":"NOW BOARDING","maxLength":24},
{"id":"flapAlphabet","type":"string","label":"Flap alphabet (drum order)","default":" ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789.,&#39;","maxLength":64},
{"id":"flipDuration","type":"number","label":"Seconds per flap","default":0.09,"min":0.03,"max":1.2,"step":0.01,"unit":"s"},
{"id":"cellStagger","type":"number","label":"Per-cell start stagger","default":0.05,"min":0,"max":0.5,"step":0.01,"unit":"s"},
{"id":"cellCount","type":"number","label":"Cells on the board","default":12,"min":1,"max":24,"step":1}
]'
>
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=1920, height=1080" />
<title>Split-Flap Board</title>
<script src="https://cdn.jsdelivr.net/npm/gsap@3.14.2/dist/gsap.min.js"></script>
<style>
*,
*::before,
*::after {
margin: 0;
padding: 0;
box-sizing: border-box;
}
html,
body {
width: 1920px;
height: 1080px;
overflow: hidden;
background: transparent;
}
</style>
</head>
<body>
<div
id="sf-root"
data-composition-id="split-flap-board"
data-start="0"
data-duration="3.5"
data-fps="30"
data-width="1920"
data-height="1080"
style="position: relative; width: 1920px; height: 1080px; overflow: hidden"
>
<style>
/* The root's own box lives in an inline style, not a rule: every
sub-composition rule is rewritten to
`[data-composition-id="split-flap-board"] <selector>` at render,
which can never match the root element itself. */
#sf-bg {
position: absolute;
inset: 0;
background:
radial-gradient(120% 90% at 50% 42%, #23242a 0%, #121317 62%, #0a0a0c 100%), #0a0a0c;
}
#sf-board {
position: absolute;
inset: 0;
display: flex;
align-items: center;
justify-content: center;
}
.sf-cell {
position: relative;
flex: 0 0 auto;
perspective: 900px;
border-radius: 9px;
background: #0c0c0e;
box-shadow:
0 18px 34px rgba(0, 0, 0, 0.55),
0 0 0 1px rgba(255, 255, 255, 0.05);
}
.sf-face {
position: absolute;
left: 0;
width: 100%;
height: 50%;
overflow: hidden;
background: linear-gradient(180deg, #26272c 0%, #1a1b1f 100%);
}
.sf-top,
.sf-leaf-a {
top: 0;
border-radius: 9px 9px 0 0;
}
.sf-bot,
.sf-leaf-b {
top: 50%;
border-radius: 0 0 9px 9px;
background: linear-gradient(180deg, #191a1e 0%, #232429 100%);
}
.sf-leaf-a {
transform-origin: 50% 100%;
z-index: 3;
backface-visibility: hidden;
}
.sf-leaf-b {
transform-origin: 50% 0%;
z-index: 3;
backface-visibility: hidden;
}
.sf-glyph {
position: absolute;
left: 0;
width: 100%;
display: block;
text-align: center;
font-family: ui-monospace, monospace;
font-weight: 700;
color: #f4efe2;
white-space: pre;
}
.sf-seam {
position: absolute;
left: 0;
top: 50%;
width: 100%;
height: 3px;
margin-top: -1.5px;
background: #050506;
z-index: 4;
}
</style>
<div id="sf-bg"></div>
<div id="sf-board" class="clip" data-start="0" data-duration="3.5" data-track-index="0"></div>
<script>
(function () {
window.__timelines = window.__timelines || {};
// ---------------------------------------------------------------
// Reference numbers (see report / research entry F#1)
//
// Alphabet: the 40-position drum from the scottbez1/splitflap
// project (Apache-2.0, README read) — blank, A-Z, 0-9, then `.,'`.
// Drum order is what makes the cascade read as a real board: a cell
// never jumps, it walks the drum forward through every intervening
// character, so letters resolve early and digits/punctuation late.
//
// Flip duration: the only published-ish figure is a DIY firmware
// proxy (28BYJ-48 stepper, ~83.59 steps/flap, a=500 steps/s^2 ->
// triangular profile -> ~1.16 s/flap). That is a hobby build, NOT a
// Solari spec, and real boards audibly flutter at tens of ms per
// flap. The default below sits in that observed band; the DIY proxy
// is still reachable at the top of the `flipDuration` range.
//
// Flap fall: constant angular acceleration through 180 degrees,
// theta(p) = 180 * p^2. The flap therefore hangs near the top and
// slaps down — no ease-out, because a falling leaf does not
// decelerate. The two CSS leaves are the two faces of that one flap
// (hand-off at theta = 90, i.e. p = 0.707).
// ---------------------------------------------------------------
var DEFAULT_ALPHABET = " ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789.,'";
var DEG = Math.PI / 180;
function num(value, min, max, fallback) {
var n = typeof value === "number" ? value : parseFloat(value);
if (!isFinite(n)) return fallback;
return Math.min(max, Math.max(min, n));
}
var vars =
window.__hyperframes && window.__hyperframes.getVariables
? window.__hyperframes.getVariables()
: {};
var alphabet = String(vars.flapAlphabet || DEFAULT_ALPHABET);
if (alphabet.length < 2) alphabet = DEFAULT_ALPHABET;
var N = alphabet.length;
var flipDur = num(vars.flipDuration, 0.03, 1.2, 0.09);
var stagger = num(vars.cellStagger, 0, 0.5, 0.05);
var cellCount = Math.round(num(vars.cellCount, 1, 24, 12));
var text = String(vars.boardText == null ? "NOW BOARDING" : vars.boardText)
.toUpperCase()
.slice(0, cellCount);
// Centre the string across the board; unused cells stay on the
// drum's first position (blank in the default alphabet).
var lead = Math.floor((cellCount - text.length) / 2);
var targets = [];
for (var i = 0; i < cellCount; i++) {
var ch =
i >= lead && i < lead + text.length ? text.charAt(i - lead) : alphabet.charAt(0);
var g = alphabet.indexOf(ch);
targets.push(g < 0 ? 0 : g);
}
// Geometry: fit `cellCount` cells across 1920 with a 120px margin.
var GAP = 10;
var cw = Math.min(130, Math.floor((1920 - 240 - (cellCount - 1) * GAP) / cellCount));
var chh = Math.round(cw * 1.45);
var board = document.getElementById("sf-board");
board.style.gap = GAP + "px";
function makeFace(cls, glyphTop) {
var face = document.createElement("div");
face.className = "sf-face " + cls;
var glyph = document.createElement("span");
glyph.className = "sf-glyph";
glyph.style.height = chh + "px";
glyph.style.lineHeight = chh + "px";
glyph.style.fontSize = Math.round(cw * 0.78) + "px";
glyph.style.top = glyphTop + "px";
face.appendChild(glyph);
return face;
}
var cells = [];
for (var c = 0; c < cellCount; c++) {
var cell = document.createElement("div");
cell.className = "sf-cell";
cell.id = "sf-cell-" + c;
cell.style.width = cw + "px";
cell.style.height = chh + "px";
// The mechanism IS clipped, stacked half-glyphs: each face holds a
// whole character and shows half of it, and the falling leaf sits
// on top of the face behind it. Declared intentional so the layout
// auditor reports real regressions instead of the design.
cell.setAttribute("data-layout-allow-overlap", "");
cell.setAttribute("data-layout-allow-occlusion", "");
cell.setAttribute("data-layout-allow-overflow", "");
var top = makeFace("sf-top", 0);
var bot = makeFace("sf-bot", -Math.round(chh / 2));
var leafA = makeFace("sf-leaf-a", 0);
var leafB = makeFace("sf-leaf-b", -Math.round(chh / 2));
var seam = document.createElement("div");
seam.className = "sf-seam";
cell.appendChild(top);
cell.appendChild(bot);
cell.appendChild(leafA);
cell.appendChild(leafB);
cell.appendChild(seam);
board.appendChild(cell);
cells.push({
// steps is unidirectional: the drum only ever spins forward,
// start position is always the drum's first flap (index 0).
steps: targets[c],
top: top.firstChild,
bot: bot.firstChild,
leafA: leafA,
leafB: leafB,
glyphA: leafA.firstChild,
glyphB: leafB.firstChild,
});
}
// A face that is not in use must be wiped, not merely hidden.
// Leaving a stale transform/filter/glyph on an opacity-0 leaf makes
// the DOM (and, via layer promotion, the rasterised pixels) depend
// on which frames were visited before this one — the exact failure
// seeking is supposed to be immune to.
function clearLeaf(leaf, glyph) {
leaf.style.opacity = "0";
leaf.style.transform = "";
leaf.style.filter = "";
glyph.textContent = "";
}
function showLeaf(leaf, glyph, char, angle, shade) {
glyph.textContent = char;
leaf.style.opacity = "1";
leaf.style.transform = "rotateX(" + angle.toFixed(2) + "deg)";
leaf.style.filter = "brightness(" + shade + ")";
}
// Pure function of absolute composition time. No accumulator, no
// dependence on the previous frame — seeking to any t reconstructs
// the whole board from t alone.
function paint(t) {
for (var i = 0; i < cells.length; i++) {
var cell = cells[i];
var tLocal = t - i * stagger;
var raw = tLocal <= 0 ? 0 : tLocal / flipDur;
var count = Math.floor(raw);
var p = raw - count;
if (count >= cell.steps) {
count = cell.steps;
p = 0;
}
var outgoing = alphabet.charAt(count % N);
var incoming = alphabet.charAt((count + 1) % N);
var flipping = count < cell.steps && p > 0;
if (!flipping) {
cell.top.textContent = outgoing;
cell.bot.textContent = outgoing;
clearLeaf(cell.leafA, cell.glyphA);
clearLeaf(cell.leafB, cell.glyphB);
continue;
}
// The new character is already seated behind the falling flap:
// its top half shows, its bottom half is still hidden by the
// outgoing flap lying in the lower slot.
cell.top.textContent = incoming;
cell.bot.textContent = outgoing;
var theta = 180 * p * p;
var shade = (1 - 0.5 * Math.sin(theta * DEG)).toFixed(3);
if (theta < 90) {
showLeaf(cell.leafA, cell.glyphA, outgoing, -theta, shade);
clearLeaf(cell.leafB, cell.glyphB);
} else {
clearLeaf(cell.leafA, cell.glyphA);
showLeaf(cell.leafB, cell.glyphB, incoming, 180 - theta, shade);
}
}
}
var duration = parseFloat(document.getElementById("sf-root").dataset.duration) || 8;
// GSAP suppresses events on seek(), so onUpdate callbacks never fire
// during a render. A property setter on the tweened driver always
// runs, because GSAP writes the value itself.
var driverTime = 0;
var driver = {};
Object.defineProperty(driver, "t", {
configurable: true,
get: function () {
return driverTime;
},
set: function (value) {
driverTime = value;
paint(value);
},
});
var tl = gsap.timeline({ paused: true });
tl.to(driver, { t: duration, duration: duration, ease: "none" }, 0);
paint(0);
window.__timelines["split-flap-board"] = tl;
})();
</script>
</div>
</body>
</html>
```
</Accordion>
{/* hf:generated-footer */}
Tagged `text` `kinetic` `mechanical` `split-flap` `solari` `departure-board` `reveal`.
## Related topics
- [Browse the complete Catalog](/catalog)
- [Add assets and Catalog items in Studio](/studio/assets-and-blocks)
- [Build a richer composition](/go-further)