/* === SITE-13: Bybit Options Academy — Professional Finance Academy === */
@font-face{font-family:'Inter';src:url('../assets/fonts/Inter-latin.woff2') format('woff2');font-weight:100 900;font-display:swap}
*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}
:root{
  --bg:#F6F4F0;--surface:#FFFFFF;--surface-alt:#EDE8E0;--surface-dim:#FAF8F5;
  --ink:#1A1A2C;--ink-2:#4A4A5C;--ink-3:#7A7A8C;
  --primary:#8B2252;--primary-light:#A63368;--primary-dim:#6E1A41;--primary-glow:rgba(139,34,82,.15);
  --accent:#F7A600;--accent-dim:#D49000;--accent-light:#FFD166;
  --gold:#C5A55A;--gold-dim:#A8893F;--gold-light:#E0C983;
  --success:#22C55E;--danger:#EF4444;--warn:#EAB308;
  --border:#DDD8CE;--border-light:#EAE6DE;
  --radius:8px;--radius-lg:14px;--radius-xl:20px;
  --font:'Inter',-apple-system,BlinkMacSystemFont,'Segoe UI','PingFang SC','Microsoft YaHei',sans-serif;
  --mono:ui-monospace,SFMono-Regular,Menlo,monospace;
  --max-w:1080px;--gap:24px;
  --shadow-sm:0 1px 3px rgba(26,26,44,.06);
  --shadow-md:0 4px 12px rgba(26,26,44,.08);
  --shadow-lg:0 8px 30px rgba(26,26,44,.1);
}
html{scroll-behavior:smooth;-webkit-text-size-adjust:100%}
body{font-family:var(--font);font-size:16px;font-weight:400;line-height:1.7;color:var(--ink);background:var(--bg);overflow-x:hidden;-webkit-font-smoothing:antialiased}
a{color:var(--primary);text-decoration:none;transition:color .2s}
a:hover{color:var(--primary-light)}
img{max-width:100%;display:block}
button{cursor:pointer;font:inherit}
ul,ol{padding-left:1.5em}
.sr-only{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap}

/* Layout */
.shell{max-width:var(--max-w);margin:0 auto;padding:0 24px}
.editorial{display:grid;grid-template-columns:1fr 1fr;gap:48px;align-items:start}
.editorial--rev{direction:rtl}
.editorial--rev>*{direction:ltr}

/* ---- Masthead ---- */
.masthead{position:sticky;top:0;z-index:100;background:rgba(246,244,240,.95);backdrop-filter:blur(12px);border-bottom:1px solid var(--border-light)}
.masthead__inner{display:flex;align-items:center;height:56px;gap:24px}
.brand{display:flex;align-items:center;gap:8px;color:var(--ink);font-weight:700;font-size:16px;text-decoration:none;flex-shrink:0}
.brand:hover{color:var(--ink)}
.brand__sub{color:var(--primary)}
.brand__mark{width:28px;height:28px}
.mastnav{display:flex;gap:20px;margin-left:auto}
.mastnav a{color:var(--ink-3);font-size:14px;font-weight:500;transition:color .2s;padding:4px 0}
.mastnav a:hover,.mastnav a.is-active{color:var(--ink)}
.mastnav a.is-active{border-bottom:2px solid var(--primary);padding-bottom:2px}
.mastactions{display:flex;gap:12px;align-items:center}
.lang-select{background:var(--surface);color:var(--ink-3);border:1px solid var(--border);border-radius:var(--radius);padding:4px 8px;font-size:13px;outline:none}
.menu-btn{display:none;background:none;border:none;color:var(--ink);width:32px;height:32px;font-size:20px}

/* ---- Typography ---- */
.section__eyebrow{font-size:11px;font-weight:600;text-transform:uppercase;letter-spacing:.1em;color:var(--primary);margin-bottom:8px}
.section__title{font-size:clamp(24px,3.5vw,36px);font-weight:700;color:var(--ink);margin-bottom:12px;line-height:1.2;letter-spacing:-.01em}
.section__lead{color:var(--ink-2);max-width:600px;line-height:1.7;margin-bottom:32px;font-size:17px}
.greek-letter{font-weight:800;font-size:20px;color:var(--primary);font-family:var(--mono)}
.diagram-label{font-weight:500;font-size:12px;color:var(--ink-3);text-transform:uppercase;letter-spacing:.06em}
.curriculum-tag{font-weight:600;font-size:11px;text-transform:uppercase;letter-spacing:.08em;padding:3px 10px;border-radius:99px;display:inline-block}
.curriculum-tag--beginner{background:rgba(34,197,94,.12);color:#16a34a}
.curriculum-tag--intermediate{background:rgba(247,166,0,.12);color:#d49000}
.curriculum-tag--advanced{background:rgba(139,34,82,.12);color:var(--primary)}

/* ---- Buttons ---- */
.btn{display:inline-flex;align-items:center;gap:8px;padding:12px 24px;border-radius:var(--radius);font-weight:600;font-size:14px;border:none;transition:all .25s;text-decoration:none}
.btn--primary{background:var(--primary);color:#fff}
.btn--primary:hover{background:var(--primary-dim);color:#fff;box-shadow:0 4px 20px var(--primary-glow);transform:translateY(-1px)}
.btn--accent{background:var(--accent);color:#000}
.btn--accent:hover{background:var(--accent-dim);color:#000;transform:translateY(-1px)}
.btn--ghost{background:transparent;color:var(--ink);border:1px solid var(--border)}
.btn--ghost:hover{border-color:var(--primary);color:var(--primary)}
.btn--gold{background:linear-gradient(135deg,var(--gold),var(--gold-dim));color:#fff}
.btn--gold:hover{background:linear-gradient(135deg,var(--gold-light),var(--gold));color:#fff;transform:translateY(-1px)}
.btn--sm{padding:8px 16px;font-size:13px}

/* ---- Hero ---- */
.hero{padding:64px 0 48px;position:relative;overflow:hidden;background:linear-gradient(180deg,var(--surface-dim) 0%,var(--bg) 100%)}
.hero::before{content:'';position:absolute;top:-60px;right:-80px;width:360px;height:360px;background:radial-gradient(circle,var(--primary-glow),transparent 70%);pointer-events:none}
.hero::after{content:'';position:absolute;bottom:-40px;left:-60px;width:280px;height:280px;background:radial-gradient(circle,rgba(197,165,90,.1),transparent 70%);pointer-events:none}
.hero__inner{display:grid;grid-template-columns:1fr 1fr;gap:48px;align-items:center;position:relative;z-index:1}
.hero__text h1{font-size:clamp(32px,4.5vw,52px);font-weight:700;line-height:1.1;margin-bottom:16px;color:var(--ink);letter-spacing:-.02em}
.hero__text h1 span{color:var(--primary)}
.hero__text p{color:var(--ink-2);font-size:17px;max-width:480px;margin-bottom:28px;line-height:1.7}
.hero__ctas{display:flex;gap:12px;flex-wrap:wrap;margin-bottom:32px}

/* Hero Payoff Diagram (CSS rendered) */
.hero-diagram{position:relative;background:var(--surface);border:1px solid var(--border);border-radius:var(--radius-lg);padding:24px;box-shadow:var(--shadow-md)}
.hero-diagram__title{font-size:14px;font-weight:600;color:var(--ink-2);margin-bottom:16px;display:flex;align-items:center;gap:8px}
.hero-diagram__canvas{position:relative;width:100%;height:260px;border-left:2px solid var(--ink-3);border-bottom:2px solid var(--ink-3);margin-left:40px;margin-bottom:32px}
.hero-diagram__axis-label{font-size:11px;font-weight:500;color:var(--ink-3);position:absolute}
.hero-diagram__axis-label--x{bottom:-24px;left:50%;transform:translateX(-50%)}
.hero-diagram__axis-label--y{top:50%;left:-36px;transform:rotate(-90deg) translateX(-50%);transform-origin:center}
.hero-diagram__zero{position:absolute;bottom:50%;left:0;right:0;border-top:1px dashed var(--ink-3)}
.hero-diagram__curve{position:absolute;top:0;bottom:0;left:0;right:0;overflow:hidden}
.hero-diagram__svg{width:100%;height:100%}
.hero-diagram__legend{display:flex;gap:16px;justify-content:center;margin-top:12px}
.hero-diagram__legend span{font-size:12px;font-weight:500;color:var(--ink-2);display:flex;align-items:center;gap:6px}
.hero-diagram__legend span::before{content:'';width:16px;height:3px;border-radius:2px}
.hero-diagram__legend span:nth-child(1)::before{background:var(--primary)}
.hero-diagram__legend span:nth-child(2)::before{background:var(--accent)}
.hero-diagram__legend span:nth-child(3)::before{background:var(--ink-3)}

/* ---- Difficulty Tabs ---- */
.diff-tabs{display:flex;gap:8px;margin-top:16px}
.diff-tab{padding:10px 20px;border-radius:var(--radius);font-size:13px;font-weight:600;border:1px solid var(--border);background:var(--surface);color:var(--ink-2);cursor:pointer;transition:all .2s}
.diff-tab:hover{border-color:var(--primary);color:var(--primary)}
.diff-tab.is-active{background:var(--primary);color:#fff;border-color:var(--primary)}

/* ---- Sections ---- */
.section{padding:60px 0}
.section--surface{background:var(--surface);border-top:1px solid var(--border-light);border-bottom:1px solid var(--border-light)}
.section--warm{background:linear-gradient(180deg,var(--bg),var(--surface-alt))}

/* ---- Curriculum Cards ---- */
.curriculum-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:24px}
.curriculum-card{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius-lg);padding:28px;transition:transform .25s,box-shadow .25s,border-color .25s}
.curriculum-card:hover{transform:translateY(-4px);box-shadow:var(--shadow-lg);border-color:var(--gold)}
.curriculum-card__head{display:flex;justify-content:space-between;align-items:center;margin-bottom:12px}
.curriculum-card__num{font-family:var(--mono);font-size:13px;color:var(--gold);font-weight:600}
.curriculum-card__title{font-size:18px;font-weight:700;color:var(--ink);margin-bottom:8px}
.curriculum-card__desc{color:var(--ink-2);font-size:14px;line-height:1.7;margin-bottom:16px}
.curriculum-card__topics{list-style:none;padding:0}
.curriculum-card__topics li{font-size:13px;color:var(--ink-3);padding:4px 0;border-bottom:1px solid var(--border-light);display:flex;align-items:center;gap:8px}
.curriculum-card__topics li::before{content:'';width:4px;height:4px;border-radius:50%;background:var(--gold);flex-shrink:0}
.curriculum-card__topics li:last-child{border-bottom:none}
.curriculum-card__cta{margin-top:16px}

/* ---- Interactive Payoff Diagram ---- */
.payoff-section{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius-xl);padding:32px;box-shadow:var(--shadow-md)}
.payoff__grid{display:grid;grid-template-columns:320px 1fr;gap:32px}
.payoff__controls{display:flex;flex-direction:column;gap:16px}
.payoff__control-group label{display:block;font-size:13px;font-weight:500;color:var(--ink-2);margin-bottom:6px}
.payoff__control-group select,.payoff__control-group input{width:100%;padding:10px 12px;background:var(--bg);color:var(--ink);border:1px solid var(--border);border-radius:var(--radius);font-size:14px;font-family:var(--mono);outline:none;transition:border-color .2s}
.payoff__control-group select:focus,.payoff__control-group input:focus{border-color:var(--primary)}
.payoff__toggle{display:flex;gap:8px}
.payoff__toggle button{flex:1;padding:10px;border-radius:var(--radius);font-size:14px;font-weight:600;border:1px solid var(--border);background:var(--bg);color:var(--ink-2);transition:all .2s}
.payoff__toggle button.is-active{background:var(--primary);color:#fff;border-color:var(--primary)}
.payoff__toggle button:hover:not(.is-active){border-color:var(--primary);color:var(--primary)}
.payoff__slider{position:relative}
.payoff__slider input[type=range]{-webkit-appearance:none;width:100%;height:6px;border-radius:3px;background:var(--border);outline:none}
.payoff__slider input[type=range]::-webkit-slider-thumb{-webkit-appearance:none;width:20px;height:20px;border-radius:50%;background:var(--primary);cursor:pointer;border:3px solid #fff;box-shadow:var(--shadow-sm)}
.payoff__slider input[type=range]::-moz-range-thumb{width:20px;height:20px;border-radius:50%;background:var(--primary);cursor:pointer;border:3px solid #fff}
.payoff__value{font-family:var(--mono);font-size:13px;color:var(--primary);font-weight:600;margin-top:4px}
.payoff__chart-area{position:relative}
.payoff__chart{position:relative;width:100%;height:320px;border-left:2px solid var(--ink);border-bottom:2px solid var(--ink);margin-left:48px}
.payoff__chart-zero{position:absolute;left:0;right:0;top:50%;border-top:1px dashed var(--ink-3)}
.payoff__chart svg{position:absolute;top:0;left:0;width:100%;height:100%}
.payoff__chart-labels{font-size:11px;color:var(--ink-3);font-weight:500}
.payoff__chart-labels .x-label{position:absolute;bottom:-24px;transform:translateX(-50%)}
.payoff__chart-labels .y-label{position:absolute;left:-48px;transform:translateY(50%);text-align:right;width:40px}
.payoff__metrics{display:grid;grid-template-columns:repeat(3,1fr);gap:12px;margin-top:16px}
.payoff__metric{background:var(--bg);border:1px solid var(--border-light);border-radius:var(--radius);padding:14px;text-align:center}
.payoff__metric-label{font-size:11px;font-weight:600;text-transform:uppercase;letter-spacing:.06em;color:var(--ink-3);margin-bottom:4px}
.payoff__metric-value{font-family:var(--mono);font-size:18px;font-weight:700;color:var(--ink)}
.payoff__metric-value--green{color:#16a34a}
.payoff__metric-value--red{color:#dc2626}

/* Payoff Tooltip */
.payoff__tooltip{position:absolute;background:var(--ink);color:#fff;font-size:12px;font-family:var(--mono);padding:6px 10px;border-radius:6px;pointer-events:none;opacity:0;transition:opacity .15s;z-index:10;white-space:nowrap}
.payoff__tooltip.is-visible{opacity:1}
.payoff__tooltip::after{content:'';position:absolute;top:100%;left:50%;transform:translateX(-50%);border:5px solid transparent;border-top-color:var(--ink)}

/* ---- Greeks Section ---- */
.greeks-grid{display:grid;grid-template-columns:repeat(5,1fr);gap:16px}
.greek-card{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius-lg);padding:20px;text-align:center;transition:transform .2s,box-shadow .2s}
.greek-card:hover{transform:translateY(-2px);box-shadow:var(--shadow-md)}
.greek-card__symbol{font-family:var(--mono);font-size:32px;font-weight:800;color:var(--primary);margin-bottom:8px}
.greek-card__name{font-size:13px;font-weight:600;color:var(--ink);margin-bottom:6px}
.greek-card__desc{font-size:12px;color:var(--ink-3);line-height:1.5}
.greek-card__meter{margin-top:12px;height:4px;background:var(--border);border-radius:2px;overflow:hidden}
.greek-card__meter-fill{height:100%;background:var(--primary);border-radius:2px;transition:width .6s ease}

/* ---- FAQ ---- */
.faq-list{max-width:720px}
.faq-item{border:1px solid var(--border-light);border-radius:var(--radius);margin-bottom:12px;overflow:hidden;transition:border-color .2s}
.faq-item:hover{border-color:var(--gold)}
.faq-item.is-open{border-color:var(--primary)}
.faq-q{display:flex;justify-content:space-between;align-items:center;padding:16px 20px;background:var(--surface);cursor:pointer;font-weight:600;font-size:15px;color:var(--ink);border:none;width:100%;text-align:left}
.faq-q:hover{color:var(--primary)}
.faq-q::after{content:'+';font-size:20px;color:var(--ink-3);transition:transform .2s;flex-shrink:0;margin-left:12px}
.faq-item.is-open .faq-q::after{content:'\2212';color:var(--primary)}
.faq-a{max-height:0;overflow:hidden;transition:max-height .3s ease}
.faq-a__inner{padding:0 20px 16px;color:var(--ink-2);font-size:14px;line-height:1.7}

/* ---- CTA Banner ---- */
.cta-banner{background:linear-gradient(135deg,var(--primary),var(--primary-dim));color:#fff;border-radius:var(--radius-xl);padding:48px;text-align:center;margin-top:16px}
.cta-banner__title{font-size:clamp(24px,3vw,36px);font-weight:700;margin-bottom:12px}
.cta-banner__text{font-size:16px;opacity:.9;margin-bottom:28px;max-width:560px;margin-left:auto;margin-right:auto}
.cta-banner__actions{display:flex;gap:12px;justify-content:center;flex-wrap:wrap}
.cta-banner .btn--accent{background:var(--accent)}
.cta-banner .btn--accent:hover{background:var(--accent-dim)}

/* ---- Footer ---- */
.footer{background:var(--ink);color:rgba(255,255,255,.6);padding:48px 0 32px;margin-top:60px}
.footer__grid{display:grid;grid-template-columns:2fr 1fr 1fr 1fr;gap:32px;margin-bottom:32px}
.footer__brand{font-size:16px;font-weight:700;color:#fff;margin-bottom:8px}
.footer__desc{font-size:13px;line-height:1.6;max-width:280px}
.footer__col-title{font-size:12px;font-weight:600;text-transform:uppercase;letter-spacing:.08em;color:rgba(255,255,255,.4);margin-bottom:12px}
.footer__links{list-style:none;padding:0}
.footer__links li{margin-bottom:8px}
.footer__links a{color:rgba(255,255,255,.6);font-size:13px;transition:color .2s}
.footer__links a:hover{color:var(--accent)}
.footer__bottom{border-top:1px solid rgba(255,255,255,.1);padding-top:24px;display:flex;justify-content:space-between;align-items:center;font-size:12px}
.footer__disclaimer{max-width:680px;font-size:11px;line-height:1.6;color:rgba(255,255,255,.35)}

/* ---- Subpage layout ---- */
.page-header{padding:48px 0 32px;background:linear-gradient(180deg,var(--surface-dim),var(--bg));border-bottom:1px solid var(--border-light)}
.page-header h1{font-size:clamp(28px,4vw,44px);font-weight:700;color:var(--ink);margin-bottom:8px}
.page-header p{color:var(--ink-2);font-size:17px;max-width:640px;line-height:1.7}
.page-content{padding:48px 0}
.page-content h2{font-size:24px;font-weight:700;color:var(--ink);margin:32px 0 12px}
.page-content h3{font-size:20px;font-weight:600;color:var(--ink);margin:24px 0 8px}
.page-content p{color:var(--ink-2);line-height:1.7;margin-bottom:16px}
.page-content ul,.page-content ol{color:var(--ink-2);line-height:1.8;margin-bottom:16px}
.page-content li{margin-bottom:6px}
.content-block{display:grid;grid-template-columns:1fr 1fr;gap:40px;align-items:start;margin-bottom:32px}
.content-block--full{grid-template-columns:1fr}
.info-box{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius-lg);padding:20px;box-shadow:var(--shadow-sm)}
.info-box--accent{border-left:4px solid var(--accent);background:#FFFDF5}
.info-box--primary{border-left:4px solid var(--primary);background:#FEF8FA}
.info-box--warn{border-left:4px solid var(--danger);background:#FFF5F5}
.info-box__title{font-size:15px;font-weight:600;color:var(--ink);margin-bottom:8px}
.info-box__text{font-size:14px;color:var(--ink-2);line-height:1.6}
.topic-nav{display:grid;grid-template-columns:repeat(4,1fr);gap:12px;margin-bottom:40px}
.topic-nav a{display:block;padding:16px;background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);text-align:center;font-weight:600;font-size:14px;color:var(--ink);transition:all .2s}
.topic-nav a:hover{border-color:var(--primary);color:var(--primary);transform:translateY(-2px);box-shadow:var(--shadow-sm)}
.topic-nav a .topic-icon{font-size:24px;margin-bottom:8px;display:block}

/* ---- Table ---- */
.data-table{width:100%;border-collapse:collapse;font-size:14px}
.data-table th{background:var(--surface-alt);font-weight:600;font-size:12px;text-transform:uppercase;letter-spacing:.06em;color:var(--ink-3);padding:10px 16px;text-align:left;border-bottom:2px solid var(--border)}
.data-table td{padding:10px 16px;border-bottom:1px solid var(--border-light);color:var(--ink-2)}
.data-table tr:hover td{background:var(--surface-dim)}

/* ---- Inline formula ---- */
.formula{display:inline-block;font-family:var(--mono);font-size:14px;background:var(--bg);border:1px solid var(--border-light);border-radius:var(--radius);padding:4px 12px;color:var(--ink);margin:4px 0}