/* =============================================================
   WebSocket Protocol — scroll-driven animation styles
   Requires a browser with animation-timeline / view() support.
   ============================================================= */

/* --- Field colour palette ------------------------------------ */
:root {
	--ws-bit-line:           color-mix(in oklch, var(--font-color) 15%, transparent);
	--ws-color-fin:          oklch(72% 0.15 250);
	--ws-color-rsv:          oklch(68% 0.12 290);
	--ws-color-opcode:       oklch(70% 0.14 155);
	--ws-color-mask-bit:     oklch(72% 0.18 35);
	--ws-color-payload-len:  oklch(75% 0.17 85);
	--ws-color-ext-payload:  oklch(72% 0.14 65);
	--ws-color-masking-key:  oklch(70% 0.15 10);
	--ws-color-payload-data: oklch(68% 0.11 200);
}

[data-theme='light'] {
	--ws-color-fin:          oklch(85% 0.17 250);
	--ws-color-rsv:          oklch(80% 0.14 290);
	--ws-color-opcode:       oklch(85% 0.16 155);
	--ws-color-mask-bit:     oklch(85% 0.20 35);
	--ws-color-payload-len:  oklch(85% 0.18 85);
	--ws-color-ext-payload:  oklch(82% 0.15 65);
	--ws-color-masking-key:  oklch(80% 0.16 10);
	--ws-color-payload-data: oklch(84% 0.12 200);
	--ws-grid-border:        color-mix(in oklch, var(--font-color) 25%, transparent);
	--ws-grid-border-heavy:  color-mix(in oklch, var(--font-color) 55%, transparent);
	--ws-bit-line:           color-mix(in oklch, var(--font-color) 10%, transparent);
}

[data-theme='light'] .field-label {
	mix-blend-mode: normal;
}

[data-theme='light'] .branch-seg > span {
	mix-blend-mode: normal;
}

[data-theme='light'] .mask-seg {
	mix-blend-mode: normal;
}

/* --- Page structure ------------------------------------------ */
.ws-post {
	max-width: 50rem;
	margin: auto;
	padding: 0 2rem;
}

/* The scrolly section breaks out to full viewport width */
.scrolly {
	width: 99vw;
	margin-left: calc(50% - 50vw);
	padding: 0 2rem;
	box-sizing: border-box;

	display: grid;
	grid-template-columns: 1fr 1fr;
	gap: 4rem;
	align-items: start;

	/* Declare scope so step view-timelines are reachable by diagram siblings */
	timeline-scope:
		--step-box,
		--step-grid,
		--step-fin,
		--step-rsv,
		--step-opcode,
		--step-mask-bit,
		--step-payload-len,
		--step-payload-branch,
		--step-ext-payload,
		--step-masking-key,
		--step-payload-data;
}

.diagram-panel {
	position: sticky;
	top: 3rem;
	align-self: start;
	padding: 2rem 0;
}

.steps-panel {
	padding: 2rem 0;
}

/* --- Step sections — each registers a view-timeline ---------- */
.step {
	min-height: 100vh;
	display: flex;
	flex-direction: column;
	justify-content: center;
	padding: 2rem 0;
}

/* --- Step navigation arrows ---------------------------------- */
.step-nav {
	display: flex;
	justify-content: center;
	padding-top: 2rem;
}

.step-nav-btn {
	background: none;
	border: 1px solid currentColor;
	border-radius: 50%;
	color: inherit;
	cursor: pointer;
	opacity: 0.35;
	width: 2.5rem;
	height: 2.5rem;
	padding: 0;
	display: flex;
	align-items: center;
	justify-content: center;
	transition: opacity 0.2s;
}

.step-nav-btn:hover,
.step-nav-btn:focus-visible {
	opacity: 0.85;
}

.step-nav-btn svg {
	width: 1.25rem;
	height: 1.25rem;
}

.step[data-step='box']            { view-timeline-name: --step-box; }
.step[data-step='grid']           { view-timeline-name: --step-grid; }
.step[data-step='fin']            { view-timeline-name: --step-fin; }
.step[data-step='rsv']            { view-timeline-name: --step-rsv; }
.step[data-step='opcode']         { view-timeline-name: --step-opcode; }
.step[data-step='mask-bit']       { view-timeline-name: --step-mask-bit; }
.step[data-step='payload-len']    { view-timeline-name: --step-payload-len; }
.step[data-step='payload-branch'] { view-timeline-name: --step-payload-branch; }
.step[data-step='ext-payload']    { view-timeline-name: --step-ext-payload; }
.step[data-step='masking-key']    { view-timeline-name: --step-masking-key; }
.step[data-step='payload-data']   { view-timeline-name: --step-payload-data; }

/* --- The frame diagram --------------------------------------- */
.ws-frame {
	display: grid;
	grid-template-columns: repeat(32, 1fr);
	/* Row 1: bit header | Row 2: first data row | Row 3: ext-payload (collapsed)
	   Row 4: masking-key | Row 5: payload-data */
	grid-template-rows: auto 3.5rem 0px 3.5rem 3.5rem;
	overflow: hidden;
	position: relative; /* for ::after bit-line overlay */

	border: 2px solid var(--font-color);
	border-radius: 3px;
	font-family: monospace;
	font-size: clamp(0.4rem, 0.9vw, 0.6rem);

	/* Two animations on different timelines: appear + expand ext-payload row */
	animation-name: ws-frame-appear, ws-expand-ext-row;
	animation-fill-mode: both, both;
	animation-timing-function: ease-out, linear;
	animation-timeline: --step-box, --step-ext-payload;
	animation-range:
		entry 0%  contain 60%,
		entry 0%  contain 60%;
}

@keyframes ws-frame-appear {
	from { opacity: 0; transform: scale(0.96); }
	to   { opacity: 1; transform: scale(1); }
}

@keyframes ws-expand-ext-row {
	from { grid-template-rows: auto 3.5rem 0px   3.5rem 3.5rem; }
	to   { grid-template-rows: auto 3.5rem 3.5rem 3.5rem 3.5rem; }
}

/* Thin 1px vertical lines at every bit position (1/32 of frame width).
   Uses background tiling on a positioned overlay so it floats above field
   backgrounds without affecting grid layout or pointer events. */
.ws-frame::after {
	content: '';
	position: absolute;
	inset: 0;
	pointer-events: none;
	z-index: 2;
	background-image: linear-gradient(
		to right,
		var(--ws-bit-line) 1px,
		transparent 1px
	);
	background-size: calc(100% / 32) 100%;
	background-repeat: repeat-x;
	opacity: 0;
	animation-name: ws-show;
	animation-timing-function: linear;
	animation-fill-mode: both;
	animation-timeline: --step-grid;
	animation-range: entry 10% contain 60%;
}

/* --- Bit-number header row ----------------------------------- */
.bit-header {
	grid-column: 1 / -1;
	grid-row: 1;
	display: grid;
	grid-template-columns: subgrid;

	animation-name: ws-show;
	animation-fill-mode: both;
	animation-timing-function: linear;
	animation-timeline: --step-grid;
	animation-range: entry 10% contain 60%;
}

.bit-number {
	text-align: center;
	padding: 3px 0 2px;
	border-right: 1px solid var(--ws-grid-border);
	border-bottom: 2px solid var(--ws-grid-border-heavy);
	color: var(--font-color);
	opacity: 0.6;
	user-select: none;
}

.bit-number.byte-start {
	border-left: 2px solid var(--ws-grid-border-heavy);
	opacity: 1;
	font-weight: bold;
}

/* --- Field cells --------------------------------------------- */
/*
  Each field type carries two animations with independent timelines:
    1. ws-show-borders — tied to --step-grid  (border-color transparent → visible)
    2. ws-highlight-* — tied to its own step (background-color → field colour)

  Labels animate on the same step timeline as their field, slightly delayed.
*/
.field {
	display: flex;
	align-items: center;
	justify-content: center;
	text-align: center;
	overflow: hidden;
	min-height: 0; /* allows grid row to collapse to 0px */
	cursor: default;
	box-sizing: border-box;
	border: 1px solid transparent; /* animated by ws-show-borders */
}

/* Heavier left border at byte boundaries (no !important — let animation control color) */
.field.byte-boundary {
	border-left-width: 2px;
}

/* Full-row fields get internal byte dividers via an absolutely-positioned
   ::before overlay so the dividers can be animated independently of the
   cell's background-color (field highlight). */
.field.full-row {
	position: relative;
}

.field.full-row::before {
	content: '';
	position: absolute;
	inset: 0;
	pointer-events: none;
	background-image: linear-gradient(
		to right,
		transparent                      calc(25% - 0.5px),
		var(--ws-grid-border-heavy)      calc(25% - 0.5px),
		var(--ws-grid-border-heavy)      calc(25% + 0.5px),
		transparent                      calc(25% + 0.5px),
		transparent                      calc(50% - 0.5px),
		var(--ws-grid-border-heavy)      calc(50% - 0.5px),
		var(--ws-grid-border-heavy)      calc(50% + 0.5px),
		transparent                      calc(50% + 0.5px),
		transparent                      calc(75% - 0.5px),
		var(--ws-grid-border-heavy)      calc(75% - 0.5px),
		var(--ws-grid-border-heavy)      calc(75% + 0.5px),
		transparent                      calc(75% + 0.5px)
	);
	opacity: 0;
	animation-name: ws-show;
	animation-timing-function: linear;
	animation-fill-mode: both;
	animation-timeline: --step-grid;
	animation-range: entry 10% contain 60%;
}

.field-label {
	padding: 0.15em 0.25em;
	overflow: hidden;
	display: -webkit-box;
	-webkit-line-clamp: 3;
	-webkit-box-orient: vertical;
	line-height: 1.2;
	font-size: 0.9em;
	color: var(--font-color);
	mix-blend-mode: screen;
	text-align: center;

	/* All labels appear together when the grid is revealed — no per-field
	   label animation needed; background color does the signalling instead. */
	opacity: 0;
	animation-name: ws-show;
	animation-timing-function: linear;
	animation-fill-mode: both;
	animation-timeline: --step-grid;
	animation-range: entry 20% contain 70%;
}

/* Single-bit cells (FIN, RSV1-3, MASK): stack characters vertically so they
   fit the narrow column width without ellipsis. */
.field.single-bit .field-label {
	writing-mode: vertical-rl;
	text-orientation: upright;
	/* Override the horizontal line-clamp with vertical overflow handling */
	display: block;
	-webkit-line-clamp: unset;
	-webkit-box-orient: unset;
	overflow: hidden;
	white-space: nowrap;
	text-overflow: clip;
	letter-spacing: -0.05em;
	padding: 0.1em 0;
}

/* --- Field info bar — updated by JS on field hover ----------- */
.field-info {
	margin-top: 0.5rem;
	padding: 0.3rem 0;
	border-top: 1px solid var(--ws-grid-border);
	font-family: monospace;
	font-size: 0.78rem;
	color: var(--font-color);
	min-height: 1.6em;
	opacity: 0;
	transition: opacity 0.15s;
}

.field-info-active {
	opacity: 1;
}

/* --- Shared keyframes ---------------------------------------- */
@keyframes ws-show {
	from { opacity: 0; }
	to   { opacity: 1; }
}

@keyframes ws-show-borders {
	from { border-color: transparent; }
	to   { border-color: var(--ws-grid-border); }
}

/* For fields that sit at byte boundaries — left border gets the heavy color */
@keyframes ws-show-borders-left-heavy {
	from { border-color: transparent; }
	to   { border-color: var(--ws-grid-border); border-left-color: var(--ws-grid-border-heavy); }
}

/* Show-and-hide: fades in quickly, holds, then fades out.
   Used for overlay elements that should disappear after their step passes.
   Requires animation-fill-mode: none and default opacity: 0 on the element. */
@keyframes ws-appear-hold-fade {
	0%         { opacity: 0; }
	15%, 85%   { opacity: 1; }
	100%       { opacity: 0; }
}

/* --- Field highlight animations ----------------------------- */
/*
  Each field type carries two animations with independent timelines:
    1. ws-show-borders — tied to --step-grid  (border-color transparent → visible)
    2. ws-highlight-* — tied to its own step (background-color → field colour)

  Labels are revealed by a single shared --step-grid animation (see above).
*/

.field-fin {
	animation-name: ws-show-borders, ws-highlight-fin;
	animation-fill-mode: both, both;
	animation-timing-function: linear, linear;
	animation-timeline: --step-grid, --step-fin;
	animation-range: entry 10% contain 60%, entry 10% contain 60%;
}
@keyframes ws-highlight-fin {
	from { background-color: transparent; }
	to   { background-color: var(--ws-color-fin); }
}

.field-rsv {
	animation-name: ws-show-borders, ws-highlight-rsv;
	animation-fill-mode: both, both;
	animation-timing-function: linear, linear;
	animation-timeline: --step-grid, --step-rsv;
	animation-range: entry 10% contain 60%, entry 10% contain 60%;
}
@keyframes ws-highlight-rsv {
	from { background-color: transparent; }
	to   { background-color: var(--ws-color-rsv); }
}

.field-opcode {
	animation-name: ws-show-borders, ws-highlight-opcode;
	animation-fill-mode: both, both;
	animation-timing-function: linear, linear;
	animation-timeline: --step-grid, --step-opcode;
	animation-range: entry 10% contain 60%, entry 10% contain 60%;
}
@keyframes ws-highlight-opcode {
	from { background-color: transparent; }
	to   { background-color: var(--ws-color-opcode); }
}

.field-mask-bit {
	animation-name: ws-show-borders-left-heavy, ws-highlight-mask-bit;
	animation-fill-mode: both, both;
	animation-timing-function: linear, linear;
	animation-timeline: --step-grid, --step-mask-bit;
	animation-range: entry 10% contain 60%, entry 10% contain 60%;
}
@keyframes ws-highlight-mask-bit {
	from { background-color: transparent; }
	to   { background-color: var(--ws-color-mask-bit); }
}

.field-payload-len {
	animation-name: ws-show-borders, ws-highlight-payload-len;
	animation-fill-mode: both, both;
	animation-timing-function: linear, linear;
	animation-timeline: --step-grid, --step-payload-len;
	animation-range: entry 10% contain 60%, entry 10% contain 60%;
}
@keyframes ws-highlight-payload-len {
	from { background-color: transparent; }
	to   { background-color: var(--ws-color-payload-len); }
}

.field-ext-payload {
	animation-name: ws-show-borders-left-heavy, ws-highlight-ext-payload;
	animation-fill-mode: both, both;
	animation-timing-function: linear, linear;
	animation-timeline: --step-grid, --step-ext-payload;
	animation-range: entry 10% contain 60%, entry 0% contain 60%;
}
@keyframes ws-highlight-ext-payload {
	from { background-color: transparent; }
	to   { background-color: var(--ws-color-ext-payload); }
}

.field-masking-key {
	animation-name: ws-show-borders, ws-highlight-masking-key;
	animation-fill-mode: both, both;
	animation-timing-function: linear, linear;
	animation-timeline: --step-grid, --step-masking-key;
	animation-range: entry 10% contain 60%, entry 10% contain 60%;
}
@keyframes ws-highlight-masking-key {
	from { background-color: transparent; }
	to   { background-color: var(--ws-color-masking-key); }
}

.field-payload-data {
	animation-name: ws-show-borders, ws-highlight-payload-data;
	animation-fill-mode: both, both;
	animation-timing-function: linear, linear;
	animation-timeline: --step-grid, --step-payload-data;
	animation-range: entry 10% contain 60%, entry 10% contain 60%;
}
@keyframes ws-highlight-payload-data {
	from { background-color: transparent; }
	to   { background-color: var(--ws-color-payload-data); }
}

/* ============================================================
   Overlay panels — branch cases and masking direction
   These use fill: none so they fade away after their step exits.
   Default opacity: 0 means they're invisible outside their range.
   ============================================================ */

/* --- Shared overlay structure ------------------------------- */
.branch-cases,
.masking-direction {
	opacity: 0; /* hidden outside their animation range */
	margin-top: 0.75rem;
}

.branch-cases {
	animation-name: ws-appear-hold-fade;
	animation-timing-function: linear;
	animation-fill-mode: none;
	animation-timeline: --step-payload-branch;
	animation-range: entry 0% exit 100%;
}

.masking-direction {
	animation-name: ws-appear-hold-fade;
	animation-timing-function: linear;
	animation-fill-mode: none;
	animation-timeline: --step-mask-bit;
	animation-range: entry 0% exit 100%;
}

/* --- Branch cases ------------------------------------------- */
.branch-case {
	margin-bottom: 0.75rem;
}

.branch-case-header {
	display: flex;
	align-items: baseline;
	gap: 0.5em;
	margin-bottom: 0.25rem;
}

.branch-case-label {
	font-family: monospace;
	font-weight: bold;
	font-size: 0.82rem;
	color: var(--font-color);
}

.branch-case-note {
	font-size: 0.72rem;
	color: var(--font-color);
	opacity: 0.65;
}

.branch-case-row {
	display: flex;
	height: 2.2rem;
	border: 1px solid var(--ws-grid-border-heavy);
	border-radius: 2px;
	overflow: hidden;
}

.branch-seg {
	display: flex;
	align-items: center;
	justify-content: center;
	font-size: clamp(0.48rem, 0.9vw, 0.62rem);
	font-family: monospace;
	border-right: 1px solid var(--ws-grid-border-heavy);
	overflow: hidden;
	padding: 0 0.15em;
}

.branch-seg > span {
	overflow: hidden;
	text-overflow: ellipsis;
	white-space: nowrap;
	color: var(--font-color);
	mix-blend-mode: screen;
}

.branch-seg:last-child { border-right: none; }

.branch-seg-ext-payload  { background-color: var(--ws-color-ext-payload); }
.branch-seg-masking-key  { background-color: var(--ws-color-masking-key); }
.branch-seg-payload-data { background-color: var(--ws-color-payload-data); }

/* --- Masking direction -------------------------------------- */
.mask-dir {
	margin-bottom: 0.75rem;
}

.mask-dir-header {
	display: flex;
	align-items: baseline;
	gap: 0.5em;
	margin-bottom: 0.25rem;
}

.mask-dir-label {
	font-family: monospace;
	font-weight: bold;
	font-size: 0.82rem;
	color: var(--font-color);
}

.mask-dir-note {
	font-size: 0.72rem;
	color: var(--font-color);
	opacity: 0.65;
}

.mask-dir-row {
	display: flex;
	height: 2.2rem;
	border: 1px solid var(--ws-grid-border-heavy);
	border-radius: 2px;
	overflow: hidden;
}

.mask-seg {
	display: flex;
	align-items: center;
	justify-content: center;
	font-size: clamp(0.48rem, 0.9vw, 0.62rem);
	font-family: monospace;
	border-right: 1px solid var(--ws-grid-border-heavy);
	overflow: hidden;
	white-space: nowrap;
	padding: 0 0.15em;
	text-overflow: ellipsis;
	color: var(--font-color);
	mix-blend-mode: screen;
}

.mask-seg:last-child { border-right: none; }

.mask-seg-mask-bit      { background-color: var(--ws-color-mask-bit); }
.mask-seg-mask-bit-zero {
	/* Greyed out — MASK is unset in server frames */
	background-color: color-mix(in oklch, var(--ws-color-mask-bit) 25%, transparent);
	opacity: 0.6;
}
.mask-seg-masking-key   { background-color: var(--ws-color-masking-key); }
.mask-seg-payload-data  { background-color: var(--ws-color-payload-data); }

/* --- Opcode table ------------------------------------------- */
.opcode-table {
	width: 100%;
	border-collapse: collapse;
	font-size: 0.85rem;
	margin: 1em 0;
}

.opcode-table td,
.opcode-table th {
	padding: 0.4em 0.6em;
	border: 1px solid var(--ws-grid-border);
}

.opcode-table td:first-child {
	font-family: monospace;
	text-align: center;
	color: var(--ws-color-opcode);
	font-weight: bold;
}

/* --- HTTP exchange display ---------------------------------- */
.http-exchange {
	display: grid;
	grid-template-columns: 1fr 1fr;
	gap: 1rem;
	margin: 1.5rem 0;
}

.http-exchange figure {
	margin: 0;
}

.http-exchange figcaption {
	font-size: 0.8rem;
	color: var(--font-color);
	opacity: 0.7;
	margin-bottom: 0.4em;
}

.http-exchange pre {
	margin: 0;
	padding: 0.75rem;
	border: 1px solid var(--ws-grid-border);
	border-radius: 3px;
	font-size: 0.75rem;
	overflow-x: auto;
	line-height: 1.6;
}

/* --- Mobile ------------------------------------------------- */
@media (max-width: 700px) {
	.scrolly {
		grid-template-columns: 1fr;
		gap: 0;
		padding: 0 1rem;
	}

	.diagram-panel {
		position: static;
		padding: 1rem 0;
	}

	.step {
		min-height: 70vh;
	}

	.http-exchange {
		grid-template-columns: 1fr;
	}

	.ws-frame {
		font-size: 0.36rem;
	}
}