/* ============================================================
   Front — Shared Base Styles (v3)
   Design: Telegram-inspired premium tutorial site
   Glassmorphism header, smooth animations, dark mode
   ============================================================ */

/* ---------- CSS Variables — Telegram Blue Palette ---------- */
:root {
  --color-primary: #0088cc;
  --color-primary-dark: #006699;
  --color-primary-light: #e6f7ff;
  --color-primary-soft: #b8e8ff;
  --color-primary-glow: rgba(0,136,204,.18);
  --color-accent: #f59e0b;
  --color-accent-dark: #d97706;
  --color-accent-light: #fffbeb;
  --color-success: #10b981;
  --color-danger: #ef4444;
  --color-bg: #ffffff;
  --color-bg-secondary: #f6f9fc;
  --color-bg-tertiary: #eef2f6;
  --color-bg-card: #ffffff;
  --color-bg-hover: #edf4fa;
  --color-bg-glass: rgba(255,255,255,.84);
  --color-text: #1e293b;
  --color-text-secondary: #64748b;
  --color-text-muted: #94a3b8;
  --color-heading: #0b1e33;
  --color-border: #dde7ef;
  --color-border-light: #edf2f7;
  --color-border-hover: #c0d4e6;
  --shadow-none: 0 0 0 transparent;
  --shadow-xs: 0 1px 2px rgba(0,136,204,.04);
  --shadow-sm: 0 1px 3px rgba(0,136,204,.05), 0 1px 2px rgba(0,0,0,.03);
  --shadow-md: 0 2px 8px rgba(0,136,204,.06), 0 1px 3px rgba(0,0,0,.04);
  --shadow-lg: 0 4px 18px rgba(0,136,204,.08), 0 2px 6px rgba(0,0,0,.04);
  --shadow-xl: 0 8px 32px rgba(0,136,204,.1), 0 3px 10px rgba(0,0,0,.04);
  --shadow-card: 0 1px 2px rgba(0,0,0,.03), 0 2px 4px rgba(0,0,0,.03);
  --shadow-card-hover: 0 4px 16px rgba(0,136,204,.1), 0 2px 6px rgba(0,0,0,.05);
  --shadow-glow: 0 0 0 3px rgba(0,136,204,.15);
  --radius-xs: 4px;
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 24px;
  --radius-full: 9999px;
  --font-sans: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-mono: "JetBrains Mono", "SF Mono", "Fira Code", Consolas, monospace;
  --max-width: 1280px;
  --max-width-narrow: 800px;
  --header-height: 68px;
  --transition-fast: .15s cubic-bezier(.4,0,.2,1);
  --transition-base: .25s cubic-bezier(.4,0,.2,1);
  --transition-slow: .4s cubic-bezier(.25,.46,.45,.94);
}

[data-theme="dark"] {
  --color-primary: #2eaadc;
  --color-primary-dark: #5cc8f0;
  --color-primary-light: #0e2a3a;
  --color-primary-soft: #162c42;
  --color-primary-glow: rgba(46,170,220,.22);
  --color-accent: #fbbf24;
  --color-accent-dark: #f59e0b;
  --color-accent-light: #1a1708;
  --color-bg: #0a0e17;
  --color-bg-secondary: #111827;
  --color-bg-tertiary: #1a2332;
  --color-bg-card: #141e2d;
  --color-bg-hover: #1a2a3d;
  --color-bg-glass: rgba(10,14,23,.88);
  --color-text: #dce4ee;
  --color-text-secondary: #94a3b8;
  --color-text-muted: #64748b;
  --color-heading: #f1f5f9;
  --color-border: #1e304a;
  --color-border-light: #162032;
  --color-border-hover: #334155;
  --shadow-xs: 0 1px 2px rgba(0,0,0,.3);
  --shadow-sm: 0 1px 3px rgba(0,0,0,.35);
  --shadow-md: 0 2px 8px rgba(0,0,0,.4);
  --shadow-lg: 0 4px 18px rgba(0,0,0,.45);
  --shadow-xl: 0 8px 32px rgba(0,0,0,.5);
  --shadow-card: 0 1px 2px rgba(0,0,0,.2);
  --shadow-card-hover: 0 4px 16px rgba(46,170,220,.12), 0 2px 6px rgba(0,0,0,.3);
  --shadow-glow: 0 0 0 3px rgba(46,170,220,.25);
}

/* ---------- Reduced Motion ---------- */
@media (prefers-reduced-motion: reduce) {
  *,*::before,*::after{animation-duration:.01ms!important;animation-iteration-count:1!important;transition-duration:.01ms!important}
}

/* ---------- Import Inter font ---------- */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700;800&display=swap');

/* ---------- Reset & Base ---------- */
*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth;-webkit-text-size-adjust:100%}
body{font-family:var(--font-sans);font-size:16px;line-height:1.75;color:var(--color-text);background:var(--color-bg);-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale;overflow-x:hidden}
::selection{background:var(--color-primary-soft);color:var(--color-primary-dark)}
::-moz-selection{background:var(--color-primary-soft);color:var(--color-primary-dark)}
a{color:var(--color-primary);text-decoration:none;transition:color var(--transition-fast)}
a:hover{color:var(--color-primary-dark)}
img{max-width:100%;height:auto;display:block}
ul,ol{list-style:none}
h1,h2,h3,h4,h5,h6{color:var(--color-heading);line-height:1.3;font-weight:700;letter-spacing:-.01em}
h1{font-size:clamp(1.5rem,4vw,2.25rem)}
h2{font-size:clamp(1.25rem,3vw,1.65rem)}
h3{font-size:clamp(1.05rem,2vw,1.25rem)}
h2 .section-header-icon{display:inline-block;margin-right:.35rem;font-size:.85em;vertical-align:middle;transition:transform var(--transition-base)}
h2:hover .section-header-icon{transform:scale(1.15) rotate(-5deg)}
p{margin-bottom:1rem}
strong{font-weight:600}
code{font-family:var(--font-mono);font-size:.875em;background:var(--color-bg-tertiary);color:var(--color-primary);padding:.15em .5em;border-radius:var(--radius-xs);border:1px solid var(--color-border)}
pre{background:var(--color-bg-secondary);border:1px solid var(--color-border);border-radius:var(--radius-md);padding:1.25rem;overflow-x:auto;margin-bottom:1.5rem;font-size:.9rem;line-height:1.6}
pre code{background:none;color:var(--color-text);padding:0;border:none}
blockquote{border-left:4px solid var(--color-primary);padding:.75rem 1.25rem;margin:1.5rem 0;color:var(--color-text-secondary);background:var(--color-bg-secondary);border-radius:0 var(--radius-sm) var(--radius-sm) 0}
hr{border:none;border-top:1px solid var(--color-border);margin:2.5rem 0}

/* ---------- Container ---------- */
.container{max-width:var(--max-width);margin:0 auto;padding:0 1.5rem}
@media(max-width:768px){.container{padding:0 1rem}}

/* ---------- Buttons ---------- */
.btn{display:inline-flex;align-items:center;justify-content:center;gap:.5rem;padding:.72rem 1.75rem;border-radius:var(--radius-full);font-size:.9rem;font-weight:600;cursor:pointer;border:1.5px solid transparent;transition:all var(--transition-base);text-decoration:none;line-height:1.5;white-space:nowrap;position:relative;overflow:hidden;letter-spacing:.01em}
.btn::after{content:"";position:absolute;inset:0;background:radial-gradient(circle at center,rgba(255,255,255,.3) 0%,transparent 70%);opacity:0;transition:opacity var(--transition-base)}
.btn:hover::after{opacity:1}
.btn-primary{background:linear-gradient(135deg,var(--color-primary),var(--color-primary-dark));color:#fff;box-shadow:0 2px 12px var(--color-primary-glow)}
.btn-primary:hover{color:#fff;box-shadow:0 6px 24px var(--color-primary-glow);transform:translateY(-2px)}
.btn-outline{border-color:var(--color-border);color:var(--color-text);background:var(--color-bg-card)}
.btn-outline:hover{border-color:var(--color-primary);color:var(--color-primary);background:var(--color-primary-light);box-shadow:0 4px 16px var(--color-primary-glow)}
.btn-accent{background:linear-gradient(135deg,var(--color-accent),var(--color-accent-dark));color:#fff;box-shadow:0 2px 12px rgba(245,158,11,.25)}
.btn-accent:hover{color:#fff;box-shadow:0 6px 24px rgba(245,158,11,.4);transform:translateY(-2px)}
.btn-sm{padding:.4rem 1rem;font-size:.82rem}
.btn-lg{padding:.82rem 2.1rem;font-size:1rem}
.btn:active{transform:scale(.97)}
@media(max-width:768px){.btn{min-height:44px}.btn-lg{min-height:48px;padding:.9rem 2rem}}

/* ---------- Section Spacing ---------- */
.section{padding:5rem 0}
.section-sm{padding:3.5rem 0}
.section-alt{background:var(--color-bg-secondary);border-top:1px solid var(--color-border-light);border-bottom:1px solid var(--color-border-light);position:relative}
.section-alt::before{content:"";position:absolute;inset:0;pointer-events:none;background-image:radial-gradient(var(--color-border) .5px,transparent .5px);background-size:20px 20px;opacity:.35}
[data-theme="dark"] .section-alt::before{background-image:radial-gradient(rgba(255,255,255,.04) .5px,transparent .5px);opacity:.45}
@media(max-width:768px){.section{padding:2rem 0}.section-sm{padding:1.5rem 0}}

/* ============================================================
   HEADER — Premium Glass Morphism
   ============================================================ */
.site-header{position:sticky;top:0;z-index:100;background:var(--color-bg-glass);border-bottom:1px solid transparent;backdrop-filter:blur(24px) saturate(180%);-webkit-backdrop-filter:blur(24px) saturate(180%);transition:border-color var(--transition-base),box-shadow var(--transition-base),background var(--transition-base)}
.site-header.scrolled{border-bottom-color:var(--color-border);box-shadow:0 1px 8px rgba(0,0,0,.06);background:var(--color-bg-glass)}
[data-theme="dark"] .site-header.scrolled{box-shadow:0 1px 8px rgba(0,0,0,.3)}
.site-header .container{display:flex;align-items:center;height:var(--header-height);gap:1.5rem}
.site-logo{display:flex;align-items:center;gap:.6rem;font-weight:800;font-size:1.15rem;color:var(--color-heading);flex-shrink:0;transition:opacity var(--transition-fast)}
.site-logo:hover{opacity:.82;color:var(--color-heading)}
.site-logo img{height:32px;width:auto;border-radius:var(--radius-xs)}
.site-logo .site-name{white-space:nowrap;background:linear-gradient(135deg,var(--color-primary),#00b4d8);-webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text}
.site-nav{display:flex;align-items:center;gap:.15rem}
.site-nav a,.nav-item .nav-label{display:inline-flex;align-items:center;padding:.45rem .9rem;border-radius:var(--radius-full);font-size:.88rem;font-weight:500;color:var(--color-text-secondary);transition:all var(--transition-fast);position:relative}
.site-nav a::after,.nav-item .nav-label::after{content:"";position:absolute;bottom:.06rem;left:50%;width:0;height:2.5px;background:var(--color-primary);border-radius:2px;transform:translateX(-50%);transition:width var(--transition-base),height var(--transition-base),box-shadow var(--transition-base)}
.site-nav a:hover::after,.nav-item .nav-label:hover::after{width:calc(100% - 1.8rem)}
.site-nav a:hover,.nav-item .nav-label:hover{color:var(--color-primary);background:var(--color-bg-hover)}
.site-nav a.active,.nav-item.has-children.active>.nav-label{color:var(--color-primary);font-weight:600}
.site-nav a.active::after,.nav-item.has-children.active>.nav-label::after{width:calc(100% - .6rem);height:3px;background:linear-gradient(90deg,var(--color-primary),#00b4d8);border-radius:3px;box-shadow:0 1px 8px var(--color-primary-glow)}
.search-trigger{display:inline-flex;align-items:center;justify-content:center;width:38px;height:38px;border-radius:var(--radius-full);border:none;background:none;color:var(--color-text-secondary);cursor:pointer;transition:all var(--transition-fast);margin-left:.5rem;flex-shrink:0}
.search-trigger:hover{color:var(--color-primary);background:var(--color-bg-hover)}
.header-actions{display:inline-flex;align-items:center;gap:10px;margin-left:auto;flex-shrink:0}
.nav-download-btn{display:inline-flex;align-items:center;height:36px;padding:0 16px;border-radius:var(--radius-full);border:none;background:linear-gradient(135deg,var(--color-primary),#0077b6);color:#fff;cursor:pointer;transition:all var(--transition-base);margin-left:0;flex-shrink:0;text-decoration:none;font-size:13px;font-weight:600;white-space:nowrap;box-shadow:0 2px 8px var(--color-primary-glow)}
.nav-download-btn:hover{background:linear-gradient(135deg,var(--color-primary-dark),#005a8c);color:#fff;box-shadow:0 4px 16px var(--color-primary-glow);transform:translateY(-1px)}
[data-theme="dark"] .nav-download-btn{background:linear-gradient(135deg,var(--color-primary),#1d8fc0);box-shadow:0 2px 10px rgba(46,170,220,.3);color:#fff}
[data-theme="dark"] .nav-download-btn:hover{background:linear-gradient(135deg,var(--color-primary-dark),#3ab4e0);box-shadow:0 4px 18px rgba(46,170,220,.4)}
[data-theme="dark"] .icon-moon{display:none}
.menu-toggle{display:none;flex-direction:column;justify-content:center;align-items:center;gap:5px;width:38px;height:38px;background:none;border:none;border-radius:var(--radius-sm);cursor:pointer;padding:0;flex-shrink:0;transition:background var(--transition-fast)}
.menu-toggle:hover{background:var(--color-bg-hover)}
.menu-toggle span{display:block;width:20px;height:2px;background:var(--color-text);border-radius:1px;transition:all var(--transition-fast)}
.menu-toggle[aria-expanded="true"] span:nth-child(1){transform:translateY(7px) rotate(45deg)}
.menu-toggle[aria-expanded="true"] span:nth-child(2){opacity:0}
.menu-toggle[aria-expanded="true"] span:nth-child(3){transform:translateY(-7px) rotate(-45deg)}

.nav-item.has-children{cursor:pointer;position:relative;display:inline-flex;align-items:center;gap:.15rem}
.nav-item .nav-arrow{transition:transform var(--transition-fast);flex-shrink:0;margin-left:-.25rem}
.nav-item.has-children:hover .nav-arrow{transform:rotate(180deg)}
.submenu{position:absolute;top:calc(100% + .35rem);left:0;min-width:170px;background:var(--color-bg-card);border:1px solid var(--color-border);border-radius:var(--radius-md);box-shadow:var(--shadow-xl);padding:.4rem;opacity:0;visibility:hidden;transform:translateY(6px);transition:all var(--transition-base);z-index:110}
.nav-item.has-children:hover .submenu{opacity:1;visibility:visible;transform:translateY(0)}
.submenu a{display:block!important;padding:.5rem .9rem;border-radius:var(--radius-sm);font-size:.85rem;font-weight:500;color:var(--color-text-secondary);white-space:nowrap;transition:all var(--transition-fast)}
.submenu a:hover{color:var(--color-primary);background:var(--color-primary-light)}
.submenu a.active{color:var(--color-primary);font-weight:600;background:transparent;box-shadow:inset 3px 0 0 var(--color-primary)}

@media(max-width:768px){
  .site-nav{display:none;position:absolute;top:var(--header-height);left:0;right:0;background:var(--color-bg);border-bottom:1px solid var(--color-border);flex-direction:column;padding:1rem;gap:.5rem;box-shadow:var(--shadow-lg);border-radius:0 0 var(--radius-lg) var(--radius-lg)}
  .site-nav.open{display:flex}
  .site-nav a{width:100%;min-height:44px;display:flex;align-items:center;justify-content:flex-start;border-radius:var(--radius-md)}
  .site-nav a::after{display:none}
  .search-trigger{display:none}
  .menu-toggle{display:flex}
  .nav-item.has-children{flex-direction:column;align-items:stretch}
  .nav-item.has-children .nav-label{width:100%}
  .nav-item .nav-label::after{display:none}
  .submenu{position:static;box-shadow:none;border:none;background:transparent;opacity:1;visibility:visible;transform:none;padding:.25rem 0 .25rem 1rem;display:none}
  .nav-item.has-children:hover .submenu,.nav-item.has-children.open .submenu{display:block}
}

/* ============================================================
   FOOTER — Premium Layout
   ============================================================ */
.site-footer{background:var(--color-bg-secondary);border-top:2px solid var(--color-border-light);padding:4.5rem 0 0;margin-top:5rem;position:relative}
.site-footer::before{content:"";position:absolute;top:0;left:0;right:0;height:2px;background:linear-gradient(90deg,transparent,var(--color-primary),var(--color-accent),transparent);opacity:.5}
.footer-grid{display:grid;grid-template-columns:2fr 1fr 1fr 1fr;gap:2.5rem;padding-bottom:3rem}
.footer-brand{display:flex;align-items:center;gap:.5rem;font-weight:800;font-size:1.05rem;color:var(--color-heading);margin-bottom:1rem}
.footer-brand img{height:28px;width:auto}
.footer-col h4{font-size:.78rem;text-transform:uppercase;letter-spacing:.08em;color:var(--color-text-muted);margin-bottom:1.2rem;position:relative;display:inline-block}
.footer-col h4::after{content:"";display:block;width:24px;height:2px;background:var(--color-accent);border-radius:1px;margin-top:.35rem}
.footer-col ul li{margin-bottom:.55rem}
.footer-col ul li a{font-size:.875rem;color:var(--color-text-secondary);transition:all var(--transition-fast);display:inline-block}
.footer-col ul li a:hover{color:var(--color-primary);transform:translateX(3px)}
.footer-about p{font-size:.875rem;color:var(--color-text-secondary);line-height:1.7}
.footer-desc{font-size:.85rem;color:var(--color-text-muted);margin-top:.6rem;line-height:1.6}
.footer-social{display:flex;gap:.75rem;margin-top:1rem}
.footer-social a{display:inline-flex;align-items:center;justify-content:center;width:36px;height:36px;border-radius:var(--radius-full);border:1px solid var(--color-border);color:var(--color-text-muted);transition:all var(--transition-fast)}
.footer-social a:hover{color:var(--color-primary);border-color:var(--color-primary);background:var(--color-primary-light);transform:translateY(-2px)}
.footer-bottom{margin-top:2rem;padding:1.5rem 0;border-top:1px solid var(--color-border);display:flex;justify-content:space-between;align-items:center;flex-wrap:wrap;gap:1rem;font-size:.82rem;color:var(--color-text-muted)}
@media(max-width:1024px){.footer-grid{gap:2rem}}
@media(max-width:768px){.site-footer{margin-top:2.5rem;padding:2.5rem 0 0}.footer-grid{grid-template-columns:repeat(3,1fr);gap:2rem;padding-bottom:1.5rem}.footer-about{grid-column:1/-1}.footer-bottom{flex-direction:column;text-align:center}}
@media(max-width:480px){.footer-grid{grid-template-columns:repeat(3,1fr);gap:1.25rem}.footer-about{grid-column:1/-1}}

/* ============================================================
   BREADCRUMB — subtle background
   ============================================================ */
.breadcrumb{padding:.7rem 0;background:var(--color-bg-tertiary);border-bottom:1px solid var(--color-border-light);font-size:.83rem}
.breadcrumb a{color:var(--color-text-muted);transition:color var(--transition-fast)}
.breadcrumb a:hover{color:var(--color-primary)}
.breadcrumb .breadcrumb-sep{color:var(--color-text-muted);margin:0 .45rem;user-select:none}
.breadcrumb span{color:var(--color-text-secondary);font-weight:500}
@media(max-width:768px){.breadcrumb .container{overflow-x:auto;white-space:nowrap;-webkit-overflow-scrolling:touch;scrollbar-width:none}.breadcrumb .container::-webkit-scrollbar{display:none}}

/* ============================================================
   BACK TO TOP
   ============================================================ */
.back-to-top{position:fixed;bottom:2.5rem;right:2.5rem;width:48px;height:48px;border-radius:var(--radius-full);border:1.5px solid var(--color-border);background:var(--color-bg-card);color:var(--color-text-secondary);cursor:pointer;display:none;align-items:center;justify-content:center;box-shadow:var(--shadow-lg);transition:all var(--transition-fast);z-index:90;backdrop-filter:blur(10px);-webkit-backdrop-filter:blur(10px)}
.back-to-top:hover{color:var(--color-primary);border-color:var(--color-primary);box-shadow:0 4px 20px var(--color-primary-glow);transform:translateY(-3px)}
.back-to-top.visible{display:flex}

/* ============================================================
   READING PROGRESS BAR
   ============================================================ */
.reading-progress{position:fixed;top:0;left:0;height:3px;background:linear-gradient(90deg,var(--color-primary),#00b4d8,var(--color-accent));z-index:200;transition:width .1s linear;border-radius:0 2px 0 0;box-shadow:0 0 8px rgba(0,136,204,.3)}

/* ============================================================
   EMPTY STATE
   ============================================================ */
.empty-state{text-align:center;padding:5rem 1rem;color:var(--color-text-muted)}
.empty-icon{margin-bottom:1.2rem;color:var(--color-border);opacity:.5}
.empty-state h3{font-size:1.2rem;color:var(--color-text-secondary);margin-bottom:.5rem}
.empty-state p{font-size:.92rem;margin-bottom:1.5rem}
.empty-state .btn{margin:0 auto}

/* ============================================================
   TAG PILL — Premium pill style
   ============================================================ */
.tag-pill{display:inline-flex;align-items:center;gap:.35rem;padding:.42rem 1rem;background:var(--color-bg-secondary);border:1.5px solid var(--color-border);border-radius:var(--radius-full);font-size:.82rem;font-weight:500;color:var(--color-text-secondary);transition:all var(--transition-base);position:relative;overflow:hidden}
.tag-pill::before{content:"";position:absolute;inset:0;background:linear-gradient(135deg,var(--color-primary-light),transparent 60%);opacity:0;transition:opacity var(--transition-base)}
.tag-pill:hover{border-color:var(--color-primary);color:var(--color-primary);transform:translateY(-3px);box-shadow:0 4px 16px var(--color-primary-glow)}
.tag-pill:hover::before{opacity:1}
.tag-cloud{display:flex;flex-wrap:wrap;justify-content:center;gap:.7rem;padding:1rem 0}

/* ============================================================
   SECTION HEADER
   ============================================================ */
.section-header{display:flex;align-items:baseline;justify-content:space-between;margin-bottom:2.5rem;flex-wrap:wrap;gap:.75rem}
.section-header h2{font-size:1.65rem;font-weight:800}
.section-header p{color:var(--color-text-secondary);margin:0}
.section-header-sub{color:var(--color-text-secondary);margin:0}
.section-more{font-size:.9rem;color:var(--color-primary);font-weight:600;white-space:nowrap;transition:all var(--transition-fast)}
.section-more:hover{gap:.4rem;color:var(--color-primary-dark);letter-spacing:.02em}
@media(max-width:768px){.section-header{flex-direction:column;align-items:flex-start;margin-bottom:1.5rem}.section-header h2{font-size:clamp(1.15rem,3.5vw,1.5rem)}}

/* ============================================================
   SCROLL ANIMATION
   ============================================================ */
.animate-on-scroll{opacity:0;transform:translateY(28px);transition:opacity .65s cubic-bezier(.25,.46,.45,.94),transform .65s cubic-bezier(.25,.46,.45,.94)}
.animate-on-scroll.visible{opacity:1;transform:translateY(0)}
.animate-on-scroll.animate-delay-1{transition-delay:.08s}
.animate-on-scroll.animate-delay-2{transition-delay:.16s}
.animate-on-scroll.animate-delay-3{transition-delay:.24s}
.animate-on-scroll.animate-delay-4{transition-delay:.32s}
.animate-on-scroll.animate-delay-5{transition-delay:.4s}
.animate-on-scroll.animate-fade-in{transform:none;transition:opacity .5s ease}
.animate-on-scroll.animate-slide-left{transform:translateX(-30px);transition:opacity .6s ease,transform .6s cubic-bezier(.25,.46,.45,.94)}
.animate-on-scroll.animate-slide-left.visible{transform:translateX(0)}
.animate-on-scroll.animate-slide-right{transform:translateX(30px);transition:opacity .6s ease,transform .6s cubic-bezier(.25,.46,.45,.94)}
.animate-on-scroll.animate-slide-right.visible{transform:translateX(0)}

/* ============================================================
   HERO SUBPAGE — gradient + blur circle
   ============================================================ */
.hero-subpage{text-align:center;position:relative;overflow:hidden;padding:4rem 0 3rem;background:linear-gradient(180deg,var(--color-primary-light) 0%,rgba(230,247,255,.3) 40%,transparent 80%)}
.hero-subpage::before{content:"";position:absolute;top:-140px;left:50%;transform:translateX(-50%);width:600px;height:600px;background:radial-gradient(circle,var(--color-primary-soft) 0%,transparent 60%);border-radius:50%;filter:blur(80px);opacity:.45;pointer-events:none}
[data-theme="dark"] .hero-subpage{background:linear-gradient(180deg,rgba(14,42,58,.6) 0%,rgba(10,14,23,0) 80%)}
[data-theme="dark"] .hero-subpage::before{opacity:.3}
.hero-subpage .container{position:relative;z-index:1}
.hero-subpage h1{font-size:2.5rem;font-weight:800;letter-spacing:-.02em;margin-bottom:.6rem}
.hero-subpage .hero-subtitle{font-size:1.1rem;color:var(--color-text-secondary);max-width:620px;margin:0 auto;line-height:1.7}
@media(max-width:1024px){.hero-subpage{padding:2.5rem 0 2rem}.hero-subpage h1{font-size:clamp(1.5rem,4vw,2.25rem)}.hero-subpage::before{width:350px;height:350px;top:-80px}}
@media(max-width:768px){.hero-subpage{padding:1.5rem 0 1rem}.hero-subpage h1{font-size:1.5rem}.hero-subpage .hero-subtitle{font-size:.95rem}.hero-subpage::before{width:240px;height:240px;top:-50px}}

/* ============================================================
   FEATURES GRID — colorful icons + premium cards
   ============================================================ */
.features-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(320px,1fr));gap:1.5rem}
.feature-card{display:flex;gap:1.35rem;padding:1.85rem;background:var(--color-bg-card);border:1.5px solid var(--color-border);border-radius:var(--radius-lg);transition:all var(--transition-base);box-shadow:var(--shadow-card);position:relative;overflow:hidden}
.feature-card::before{content:"";position:absolute;top:0;left:0;right:0;height:3px;background:linear-gradient(90deg,var(--color-primary),var(--color-accent));opacity:0;transition:opacity var(--transition-base)}
.feature-card:hover{transform:translateY(-6px);box-shadow:var(--shadow-xl);border-color:var(--color-primary-soft)}
.feature-card:hover::before{opacity:1}
.feature-icon{flex-shrink:0;width:56px;height:56px;display:flex;align-items:center;justify-content:center;border-radius:var(--radius-lg);color:var(--color-primary);font-size:1.4rem;transition:all var(--transition-base)}
.feature-card:hover .feature-icon{transform:scale(1.1)}
/* 5-color gradients for icon variants */
.feature-icon{background:linear-gradient(135deg,var(--color-primary-light),var(--color-primary-soft))}
.feature-icon.accent-blue{background:linear-gradient(135deg,#dbeafe,#bfdbfe);color:#2563eb}
.feature-icon.accent-green{background:linear-gradient(135deg,#d1fae5,#a7f3d0);color:#059669}
.feature-icon.accent-orange{background:linear-gradient(135deg,#ffedd5,#fed7aa);color:#ea580c}
.feature-icon.accent-purple{background:linear-gradient(135deg,#ede9fe,#ddd6fe);color:#7c3aed}
.feature-icon.accent-cyan{background:linear-gradient(135deg,#cffafe,#a5f3fc);color:#0891b2}
[data-theme="dark"] .feature-icon.accent-blue{background:linear-gradient(135deg,rgba(37,99,235,.15),rgba(37,99,235,.25))}
[data-theme="dark"] .feature-icon.accent-green{background:linear-gradient(135deg,rgba(5,150,105,.15),rgba(5,150,105,.25))}
[data-theme="dark"] .feature-icon.accent-orange{background:linear-gradient(135deg,rgba(234,88,12,.15),rgba(234,88,12,.25))}
[data-theme="dark"] .feature-icon.accent-purple{background:linear-gradient(135deg,rgba(124,58,237,.15),rgba(124,58,237,.25))}
[data-theme="dark"] .feature-icon.accent-cyan{background:linear-gradient(135deg,rgba(8,145,178,.15),rgba(8,145,178,.25))}
.feature-card h3{font-size:1.1rem;margin-bottom:.3rem;max-width:2.2em;line-height:1.3}
.feature-card p{font-size:.875rem;color:var(--color-text-secondary);line-height:1.65;margin:0}
@media(max-width:1024px){.features-grid{grid-template-columns:repeat(auto-fill,minmax(280px,1fr))}}
@media(max-width:768px){.features-grid{grid-template-columns:repeat(auto-fill,minmax(240px,1fr))}.feature-card{padding:1.25rem}.feature-icon{width:48px;height:48px}}
@media(max-width:480px){.features-grid{grid-template-columns:1fr}}

/* ============================================================
   CTA SECTION (shared)
   ============================================================ */
.cta-section{text-align:center;margin-top:3.5rem;padding:3.5rem 2.5rem;background:linear-gradient(135deg,var(--color-primary) 0%,#6366f1 50%,#8b5cf6 100%);border-radius:var(--radius-xl);color:#fff;box-shadow:0 8px 32px rgba(99,102,241,.3);position:relative;overflow:hidden}
.cta-section::before{content:"";position:absolute;top:-50%;left:-50%;width:200%;height:200%;background:radial-gradient(circle at 30% 20%,rgba(255,255,255,.08) 0%,transparent 50%);pointer-events:none}
.cta-section h2{color:#fff;font-size:1.55rem;margin-bottom:.6rem}
.cta-section p{color:rgba(255,255,255,.85);margin-bottom:1.75rem;font-size:.98rem}
@media(max-width:1024px){.cta-section{padding:2.5rem 1.5rem}.cta-section h2{font-size:1.3rem}}
@media(max-width:768px){.cta-section{padding:2rem 1.25rem;margin-top:2rem}.cta-section h2{font-size:1.2rem}.cta-section p{font-size:.9rem}}

/* ============================================================
   UTILITY
   ============================================================ */
.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);border:0}
/* Skip to content link */
.skip-to-content{position:absolute;left:-9999px;top:0;z-index:9999;background:var(--color-primary,#2563eb);color:#fff;padding:.5rem 1rem;font-size:.9rem;text-decoration:none;border-radius:0 0 .3rem .3rem;transition:left 0s}
.skip-to-content:focus{left:.5rem}
/* Topic card stretch link */
.topic-card{position:relative}
.topic-card-link{color:inherit;text-decoration:none}
.topic-card-link::after{content:"";position:absolute;inset:0}
.text-center{text-align:center}
.hidden{display:none!important}
@media(min-width:769px){.desktop-only{display:block}.mobile-only{display:none}}
@media(max-width:768px){.desktop-only{display:none}.mobile-only{display:block}}