Install
That writes one file:compositions/split-flap-board.html.
Add it to your video
It runs for 3.5 seconds at 1920×1080. Paste this into your composition: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>
data-start. Put it on a different timeline row with
data-track-index. See 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 |
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:
<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
split-flap-board.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.,'","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>
text kinetic mechanical split-flap solari departure-board reveal.