/* Pronab Roy Series Reader — Kindle-style book view. No external assets. */
:root {
	--bk-ui: Inter, system-ui, -apple-system, "Segoe UI", Roboto, Arial, sans-serif;
	--bk-serif: Literata, Georgia, "Iowan Old Style", Charter, Cambria, "Times New Roman", serif;
	--bk-sans: Inter, system-ui, -apple-system, "Segoe UI", Roboto, Arial, sans-serif;
	--bk-mono: "JetBrains Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;
	--bk-font: var(--bk-serif);
	--bk-size: 18px;
	--bk-page-h: 600px;
	--bk-desk: #e9ecef;
	--bk-paper: #fdfcf9;
	--bk-ink: #1d2433;
	--bk-muted: #5d6676;
	--bk-line: #e2e4e8;
	--bk-teal: #0e8a7c;
	--bk-gold: #b8860b;
	--bk-bar: rgba(253, 252, 249, .96);
	--bk-code-bg: #f3f5f8;
	--bk-shadow: 0 18px 40px -18px rgba(10, 18, 36, .35), 0 2px 6px rgba(10, 18, 36, .08);
	--prsr-tok-k: #8f2bb3; --prsr-tok-s: #0a7a34; --prsr-tok-c: #6a737d; --prsr-tok-n: #b35900;
	--prsr-tok-t: #0f6a8f; --prsr-tok-f: #3a4fc6; --prsr-tok-v: #b31d28; --prsr-tok-o: #6b4bb3; --prsr-tok-pr: #1f5fbf;
	color-scheme: light;
}
[data-theme="sepia"] {
	--bk-desk: #e6dcc3; --bk-paper: #f4ecd8; --bk-ink: #3b2f20; --bk-muted: #76664f; --bk-line: #dccfb0;
	--bk-teal: #1d6f66; --bk-gold: #8a5a0b; --bk-bar: rgba(244, 236, 216, .96); --bk-code-bg: #ebe1c8;
	--prsr-tok-k: #8b2a6b; --prsr-tok-s: #4f6b12; --prsr-tok-c: #8a7a60; --prsr-tok-n: #a4480a; --prsr-tok-t: #1e6070; --prsr-tok-f: #3d4d9a; --prsr-tok-v: #a0281c; --prsr-tok-o: #6a4a8a; --prsr-tok-pr: #2d5c8a;
}
[data-theme="dark"] {
	--bk-desk: #060b17; --bk-paper: #0d1529; --bk-ink: #d8dde7; --bk-muted: #96a0b3; --bk-line: #22304d;
	--bk-teal: #20c9b4; --bk-gold: #f0be46; --bk-bar: rgba(10, 18, 36, .96); --bk-code-bg: #081022;
	--bk-shadow: 0 18px 40px -18px rgba(0, 0, 0, .8);
	--prsr-tok-k: #d2a8ff; --prsr-tok-s: #a5d6a7; --prsr-tok-c: #8b949e; --prsr-tok-n: #f2b36f; --prsr-tok-t: #79c0ff; --prsr-tok-f: #a3b6ff; --prsr-tok-v: #ff9492; --prsr-tok-o: #c6a8ff; --prsr-tok-pr: #7fb0ff;
	color-scheme: dark;
}
[data-font="sans"] { --bk-font: var(--bk-sans); }

*, *::before, *::after { box-sizing: border-box; }
html, body { height: 100%; }
body.bk {
	margin: 0; overflow: hidden; background: var(--bk-desk); color: var(--bk-ink);
	font-family: var(--bk-ui); display: grid; grid-template-rows: auto minmax(0, 1fr) auto; grid-template-columns: minmax(0, 1fr); width: 100%; height: 100vh; height: 100dvh;
	transition: background-color .25s ease, color .25s ease; -webkit-text-size-adjust: 100%;
}
a { color: var(--bk-teal); }
:focus-visible { outline: 2px solid var(--bk-gold); outline-offset: 2px; }
.bk-skip { position: absolute; left: -9999px; }
.bk-skip:focus { left: .5rem; top: .5rem; z-index: 90; background: var(--bk-gold); color: #0a1224; padding: .4rem .8rem; }

/* progress */
.bk-progress { position: fixed; top: 0; left: 0; right: 0; height: 3px; z-index: 70; }
.bk-progress__fill { display: block; height: 100%; width: 0; background: linear-gradient(90deg, var(--bk-teal), var(--bk-gold)); transition: width .3s ease; }

/* toolbar */
.bk-bar { min-width: 0; display: flex; align-items: center; gap: .25rem; padding: .45rem .6rem; background: var(--bk-bar); border-bottom: 1px solid var(--bk-line); z-index: 40; transition: transform .25s ease, opacity .25s ease; }
.bk-bar__title { flex: 1; min-width: 0; text-align: center; font-weight: 600; font-size: .9rem; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; color: var(--bk-muted); }
.bk-btn { display: inline-flex; align-items: center; gap: .35rem; min-height: 36px; min-width: 36px; justify-content: center; padding: .3rem .55rem; border: 1px solid transparent; border-radius: 9px; background: transparent; color: var(--bk-ink); font: 500 .85rem var(--bk-ui); text-decoration: none; cursor: pointer; }
.bk-btn:hover { border-color: var(--bk-line); }
.bk-btn__lbl { display: none; }
@media (min-width: 720px) { .bk-btn__lbl { display: inline; } }
.bk-ribbon svg { fill: none; stroke: currentColor; stroke-width: 2; }
.bk-ribbon[aria-pressed="true"] { color: var(--bk-gold); }
.bk-ribbon[aria-pressed="true"] svg { fill: var(--bk-gold); stroke: var(--bk-gold); }
body.bk.is-chrome-hidden .bk-bar { opacity: 0; pointer-events: none; }
body.bk.is-chrome-hidden .bk-foot { opacity: 0; pointer-events: none; }

/* settings */
.bk-settings { position: fixed; top: 52px; right: .6rem; z-index: 60; background: var(--bk-paper); color: var(--bk-ink); border: 1px solid var(--bk-line); border-radius: 14px; padding: .8rem; box-shadow: var(--bk-shadow); width: min(340px, calc(100vw - 1.2rem)); }
.bk-set__row { display: flex; align-items: center; gap: .4rem; padding: .35rem 0; flex-wrap: wrap; }
.bk-set__row[hidden] { display: none; }
.bk-set__lbl { flex: 0 0 5.2rem; font-size: .8rem; color: var(--bk-muted); text-transform: uppercase; letter-spacing: .06em; font-weight: 600; }
.bk-chip { min-height: 34px; padding: .25rem .7rem; border-radius: 999px; border: 1px solid var(--bk-line); background: transparent; color: var(--bk-ink); font: 500 .85rem var(--bk-ui); cursor: pointer; }
.bk-chip[aria-pressed="true"] { border-color: var(--bk-teal); box-shadow: inset 0 0 0 1px var(--bk-teal); color: var(--bk-teal); }
.bk-chip--serif { font-family: var(--bk-serif); }
.bk-theme--light { background: #fdfcf9; color: #1d2433; }
.bk-theme--sepia { background: #f4ecd8; color: #3b2f20; }
.bk-theme--dark { background: #0d1529; color: #d8dde7; }
.bk-theme[aria-pressed="true"] { box-shadow: 0 0 0 2px var(--bk-gold); }
.bk-size-dots { display: inline-flex; gap: 4px; }
.bk-size-dots i { width: 7px; height: 7px; border-radius: 50%; background: var(--bk-line); display: inline-block; }
.bk-size-dots i.on { background: var(--bk-teal); }

/* drawers */
.bk-scrim { position: fixed; inset: 0; background: rgba(6, 11, 23, .45); z-index: 50; }
.bk-drawer { position: fixed; top: 0; bottom: 0; left: 0; width: min(380px, 88vw); z-index: 55; background: var(--bk-paper); color: var(--bk-ink); border-right: 1px solid var(--bk-line); overflow-y: auto; padding: 0 1rem 1.5rem; box-shadow: var(--bk-shadow); }
#bk-marks-drawer { left: auto; right: 0; border-right: 0; border-left: 1px solid var(--bk-line); }
.bk-drawer__head { position: sticky; top: 0; display: flex; justify-content: space-between; align-items: center; padding: .7rem 0; background: var(--bk-paper); border-bottom: 1px solid var(--bk-line); }
.bk-toc__part { margin: 1.1rem 0 .3rem; font: 700 .72rem var(--bk-ui); letter-spacing: .12em; text-transform: uppercase; color: var(--bk-gold); }
.bk-toc__list { list-style: none; margin: .3rem 0; padding: 0; }
.bk-toc__list li { padding: .35rem 0; border-bottom: 1px dashed var(--bk-line); font-size: .92rem; line-height: 1.4; }
.bk-toc__list a { color: var(--bk-ink); text-decoration: none; display: flex; gap: .5rem; }
.bk-toc__list a:hover .bk-toc__t { color: var(--bk-teal); }
.bk-toc__num { flex: 0 0 1.6rem; color: var(--bk-teal); font-weight: 700; font-variant-numeric: tabular-nums; }
.bk-toc__list .is-soon { color: var(--bk-muted); display: flex; gap: .5rem; align-items: baseline; }
.bk-toc__t { flex: 1; min-width: 0; }
.bk-toc__list .is-soon .bk-toc__num { color: var(--bk-muted); }
.bk-toc__list em { font-size: .75rem; font-style: normal; color: var(--bk-gold); border: 1px solid currentColor; border-radius: 999px; padding: 0 .45rem; flex: 0 0 auto; white-space: nowrap; align-self: center; }
.bk-marks { list-style: none; margin: .5rem 0; padding: 0; }
.bk-marks li { display: flex; gap: .5rem; align-items: flex-start; padding: .55rem 0; border-bottom: 1px solid var(--bk-line); }
.bk-marks a { flex: 1; color: var(--bk-ink); text-decoration: none; font-size: .9rem; }
.bk-marks small { display: block; color: var(--bk-muted); }
.bk-marks button { border: 0; background: none; color: var(--bk-muted); cursor: pointer; font: inherit; font-size: .8rem; }

/* stage & book */
.bk-stage { position: relative; min-width: 0; overflow: hidden; display: flex; align-items: center; justify-content: center; padding: 14px 10px; min-height: 0; }
.bk-book { position: relative; height: 100%; width: 100%; max-width: 760px; background: var(--bk-paper); border-radius: 6px; box-shadow: var(--bk-shadow); transition: background-color .25s ease; perspective: 2000px; }
.bk-book.is-spread { max-width: 1320px; }
.bk-book.is-spread::after { content: ""; position: absolute; top: 0; bottom: 0; left: 50%; width: 46px; transform: translateX(-50%); pointer-events: none; background: linear-gradient(90deg, rgba(0,0,0,0) 0%, rgba(0,0,0,.07) 45%, rgba(0,0,0,.13) 50%, rgba(0,0,0,.07) 55%, rgba(0,0,0,0) 100%); }
.bk-viewport { position: absolute; inset: 34px 30px 30px; overflow: hidden; outline: none; }
@media (min-width: 720px) { .bk-viewport { inset: 46px 56px 40px; } }
.bk-flow {
	height: 100%; column-fill: auto; column-gap: var(--bk-gap, 60px); column-width: var(--bk-page-w, 600px);
	font-family: var(--bk-font); font-size: var(--bk-size); line-height: 1.65; color: var(--bk-ink);
	will-change: transform; transform: translate3d(0, 0, 0); hyphens: auto; -webkit-hyphens: auto; overflow-wrap: break-word;
}
.bk-flow.is-fade { animation: bk-fade .22s ease; }
@keyframes bk-fade { from { opacity: .25; } to { opacity: 1; } }

.bk-sec { break-before: column; -webkit-column-break-before: always; }
.bk-sec:first-child { break-before: auto; }
.bk-coverpage { height: 100%; display: flex; }
.bk-titlepage { height: 100%; display: flex; flex-direction: column; align-items: center; justify-content: center; text-align: center; }
.bk-titlepage__kicker { font: 600 .72rem var(--bk-ui); letter-spacing: .16em; text-transform: uppercase; color: var(--bk-teal); margin: 0; }
.bk-titlepage__title { font-size: 1.9em; line-height: 1.2; margin: .5em 0 .2em; }
.bk-rule { width: 64px; height: 3px; background: linear-gradient(90deg, var(--bk-teal), var(--bk-gold)); margin: .8em auto; display: block; border-radius: 2px; }
.bk-titlepage__author { font-style: italic; font-size: 1.1em; margin: .2em 0 1em; }
.bk-titlepage__desc { font-size: .88em; color: var(--bk-muted); max-width: 30em; }
.bk-titlepage__ed, .bk-titlepage__copy { font: .75rem var(--bk-ui); color: var(--bk-muted); margin: .25rem 0; }
.bk-titlepage__ed { margin-top: 2.5em; }
.bk-tocpage__h { font-family: var(--bk-ui); font-size: 1.05em; letter-spacing: .14em; text-transform: uppercase; color: var(--bk-teal); margin: 0 0 .5em; }
.bk-tocpage .bk-toc__list li { font-size: .82em; }

/* covers (shared with shelf) */
.prsr-cover { position: relative; width: 100%; height: 100%; overflow: hidden; border-radius: 4px; }
.prsr-cover img { display: block; width: 100%; height: 100%; object-fit: cover; }
.prsr-cover--generated { background: radial-gradient(120% 80% at 80% 0%, rgba(32,201,180,.35), transparent 60%), radial-gradient(90% 60% at 0% 100%, rgba(240,190,70,.28), transparent 60%), #0a1224; color: #fff; display: flex; flex-direction: column; justify-content: center; padding: 12% 10%; font-family: var(--bk-ui); border: 1px solid rgba(240,190,70,.45); }
.prsr-cover__kicker { font-size: .7rem; letter-spacing: .18em; text-transform: uppercase; color: #20c9b4; font-weight: 700; }
.prsr-cover__title { font-size: 1.6rem; font-weight: 800; line-height: 1.15; margin: .6rem 0; }
.prsr-cover__rule { display: block; width: 48px; height: 3px; background: #f0be46; margin: .5rem 0 1rem; }
.prsr-cover__author { font-size: .85rem; color: #f0be46; font-weight: 600; }
.bk-cover { box-shadow: 0 6px 20px rgba(0,0,0,.25); }
.prsr-cover--image { background: radial-gradient(120% 80% at 80% 0%, rgba(32,201,180,.3), transparent 60%), #0a1224; color: #fff; display: flex; flex-direction: column; font-family: var(--bk-ui); border: 1px solid rgba(240,190,70,.45); }
.prsr-cover--image .prsr-cover__art { flex: 0 0 auto; padding: 8% 8% 0; }
.prsr-cover--image img { width: 100%; height: auto; max-height: none; object-fit: contain; border-radius: 4px; box-shadow: 0 10px 24px rgba(0,0,0,.45); }
.prsr-cover--image .prsr-cover__text { flex: 1; display: flex; flex-direction: column; justify-content: center; padding: 6% 9% 9%; }

/* chapter */
.bk-chapter__head { margin: 0 0 1.4em; padding-top: 1.2em; }
.bk-chapter__num { font: 700 .72rem var(--bk-ui); letter-spacing: .14em; text-transform: uppercase; color: var(--bk-gold); margin: 0 0 .5em; }
.bk-chapter__title { font-size: 1.6em; line-height: 1.2; margin: 0; break-after: avoid; }
.bk-chapter__head::after { content: ""; display: block; width: 56px; height: 3px; margin-top: .7em; background: linear-gradient(90deg, var(--bk-teal), var(--bk-gold)); border-radius: 2px; }
.bk-chapter__foot { font: .8rem var(--bk-ui); color: var(--bk-muted); margin-top: 2em; }
.bk-content > * { max-width: 100%; }
.bk-content > h1:first-child { display: none; } /* duplicate of the chapter heading */
@media (max-width: 600px) { .bk-content p { text-align: left; hyphens: manual; } }
/* Soft-wrapped source (Markdown imports) turns line wraps into <br>; reflow them in book mode. */
.bk-content p > br, .bk-content li > br, .bk-content h2 > br, .bk-content h3 > br { display: none; }
.bk-content p { margin: 0 0 .9em; text-align: justify; orphans: 2; widows: 2; }
.bk-content h2, .bk-content h3, .bk-content h4 { font-family: var(--bk-ui); line-height: 1.25; break-after: avoid; margin: 1.3em 0 .5em; }
.bk-content h2 { font-size: 1.25em; } .bk-content h3 { font-size: 1.08em; } .bk-content h4 { font-size: 1em; }
.bk-content img, .bk-content video, .bk-content svg { max-width: 100%; max-height: calc(var(--bk-page-h) - 3em); height: auto; object-fit: contain; }
.bk-content figure { margin: 1em 0; break-inside: avoid; }
.bk-content figcaption { font: .75rem var(--bk-ui); color: var(--bk-muted); }
.bk-content blockquote { margin: 1em 0; padding: .2em 1em; border-left: 3px solid var(--bk-gold); color: var(--bk-muted); break-inside: avoid; }
.bk-content ul, .bk-content ol { padding-left: 1.4em; }
.bk-content li { margin: .2em 0; }
.bk-content code { font-family: var(--bk-mono); font-size: .84em; background: var(--bk-code-bg); padding: .08em .3em; border-radius: 4px; }
.bk-content pre { font-family: var(--bk-mono); font-size: .76em; line-height: 1.5; background: var(--bk-code-bg); border: 1px solid var(--bk-line); border-radius: 8px; padding: .8em 1em; overflow: auto; max-height: calc(var(--bk-page-h) - 2em); break-inside: avoid; white-space: pre; }
.bk-content pre code { background: none; padding: 0; font-size: 1em; }
.bk-content table { display: block; max-width: 100%; overflow: auto; border-collapse: collapse; font: .8em/1.4 var(--bk-ui); break-inside: avoid; max-height: calc(var(--bk-page-h) - 2em); }
.bk-content th, .bk-content td { border: 1px solid var(--bk-line); padding: .35em .55em; text-align: left; }
.bk-content .callout, .bk-content .is-style-tip, .bk-content .is-style-note, .bk-content .is-style-warning { border-left: 3px solid var(--bk-teal); background: var(--bk-code-bg); padding: .6em .9em; border-radius: 6px; break-inside: avoid; }
.prsr-tok-k { color: var(--prsr-tok-k); } .prsr-tok-s { color: var(--prsr-tok-s); } .prsr-tok-c { color: var(--prsr-tok-c); font-style: italic; } .prsr-tok-n { color: var(--prsr-tok-n); } .prsr-tok-t, .prsr-tok-p, .prsr-tok-a { color: var(--prsr-tok-t); } .prsr-tok-f { color: var(--prsr-tok-f); } .prsr-tok-v { color: var(--prsr-tok-v); } .prsr-tok-o { color: var(--prsr-tok-o); } .prsr-tok-pr { color: var(--prsr-tok-pr); }

/* CodeGround "Try it" cards */
.prsr-tryit { margin: 1em 0; border: 1px solid var(--bk-line); border-left: 4px solid var(--bk-teal); border-radius: 10px; padding: .7em .9em; background: var(--bk-code-bg); break-inside: avoid; font-family: var(--bk-ui); }
.prsr-tryit__head { margin: 0 0 .4em; font-size: .72rem; letter-spacing: .1em; text-transform: uppercase; font-weight: 700; color: var(--bk-teal); }
.prsr-tryit__badge { color: var(--bk-gold); margin-left: .4em; }
.bk-content .prsr-tryit__code { margin: 0 0 .6em; max-height: 12em; background: var(--bk-paper); }
.prsr-tryit__btn { display: inline-block; font-weight: 700; font-size: .82rem; text-decoration: none; padding: .45em .9em; border-radius: 999px; background: #20c9b4; color: #0a1224 !important; }
.prsr-tryit__btn:hover { background: #f0be46; }

/* soon */
.bk-soon { text-align: center; padding-top: 25%; }

/* page curl: a 3D leaf with front/back faces cut from clones of the book */
.bk-fx { position: absolute; inset: 0; pointer-events: none; z-index: 5; perspective: 2400px; display: none; }
.bk-fx.is-on { display: block; }
.bk-under, .bk-leaf, .bk-cast { position: absolute; top: 0; bottom: 0; }
.bk-under { background: var(--bk-paper); overflow: hidden; }
.bk-fx.is-one .bk-under, .bk-fx.is-two .bk-under { border-radius: 6px; }
.bk-leaf { transform-style: preserve-3d; will-change: transform; }
.bk-face { position: absolute; inset: 0; overflow: hidden; background: var(--bk-paper); backface-visibility: hidden; -webkit-backface-visibility: hidden; }
.bk-face--back { transform: rotateY(180deg); }
.bk-win { position: absolute; overflow: hidden; }
.bk-win > .bk-flow { height: 100%; will-change: auto; }
.bk-face__shade { position: absolute; inset: 0; pointer-events: none; }
.bk-leaf.is-forward .bk-face--front .bk-face__shade { background: linear-gradient(90deg, rgba(0,0,0,.28) 0%, rgba(0,0,0,.06) 18%, rgba(255,255,255,.10) 55%, rgba(0,0,0,.16) 88%, rgba(0,0,0,.30) 100%); }
.bk-leaf.is-forward .bk-face--back .bk-face__shade { background: linear-gradient(270deg, rgba(0,0,0,.30) 0%, rgba(0,0,0,.05) 25%, rgba(255,255,255,.08) 60%, rgba(0,0,0,.18) 100%); }
.bk-leaf.is-back .bk-face--front .bk-face__shade { background: linear-gradient(270deg, rgba(0,0,0,.28) 0%, rgba(0,0,0,.06) 18%, rgba(255,255,255,.10) 55%, rgba(0,0,0,.16) 88%, rgba(0,0,0,.30) 100%); }
.bk-leaf.is-back .bk-face--back .bk-face__shade { background: linear-gradient(90deg, rgba(0,0,0,.30) 0%, rgba(0,0,0,.05) 25%, rgba(255,255,255,.08) 60%, rgba(0,0,0,.18) 100%); }
.bk-fx.is-one .bk-leaf.is-back .bk-face--front .bk-face__shade { background: linear-gradient(90deg, rgba(0,0,0,.28) 0%, rgba(0,0,0,.06) 18%, rgba(255,255,255,.10) 55%, rgba(0,0,0,.16) 88%, rgba(0,0,0,.30) 100%); }
.bk-cast { opacity: 0; }
.bk-fx.is-two .bk-leaf.is-forward ~ .bk-cast, .bk-fx .bk-cast { background: linear-gradient(90deg, rgba(0,0,0,.35), rgba(0,0,0,.08) 35%, rgba(0,0,0,0) 70%); }
.bk-book.is-turning .bk-edge { opacity: 0; }
@media (prefers-reduced-motion: reduce) { .bk-fx { display: none !important; } }

/* edge buttons */
.bk-edge { position: absolute; top: 0; bottom: 0; width: 28px; border: 0; background: transparent; cursor: pointer; z-index: 6; color: var(--bk-muted); opacity: .0; transition: opacity .2s; }
.bk-edge--prev { left: 0; } .bk-edge--next { right: 0; }
.bk-edge::before { font: 700 1.2rem var(--bk-ui); }
.bk-edge--prev::before { content: "\2039"; } .bk-edge--next::before { content: "\203A"; }
.bk-book:hover .bk-edge, .bk-edge:focus-visible { opacity: .8; }
.bk-edge[disabled] { visibility: hidden; }

/* footer */
.bk-foot { display: flex; align-items: center; gap: .8rem; padding: .4rem 1rem .55rem; font: 500 .8rem var(--bk-ui); color: var(--bk-muted); background: var(--bk-bar); border-top: 1px solid var(--bk-line); transition: opacity .25s ease; }
.bk-foot__status { white-space: nowrap; font-variant-numeric: tabular-nums; color: var(--bk-ink); }
.bk-foot__left { white-space: nowrap; display: none; }
@media (min-width: 720px) { .bk-foot__left { display: inline; } }
.bk-scrub { flex: 1; accent-color: var(--bk-teal); min-width: 60px; }

.bk-toast { position: fixed; left: 50%; bottom: 64px; transform: translateX(-50%); background: #0a1224; color: #fff; border: 1px solid #f0be46; padding: .45rem .9rem; border-radius: 999px; font: 500 .85rem var(--bk-ui); z-index: 80; }
.bk-preview { position: absolute; top: 0; left: 0; right: 0; margin: 0; text-align: center; font: .8rem var(--bk-ui); background: #f0be46; color: #0a1224; z-index: 10; }
.bk-noscript { font-family: var(--bk-ui); }
:fullscreen body.bk, body.bk:fullscreen { background: var(--bk-desk); }