/* ===== Design Tokens ===== */
:root {
  --bg: #09090b;
  --bg-secondary: #111113;
  --bg-tertiary: #1a1a1f;
  --bg-card: #141418;
  --bg-card-hover: #1c1c22;
  --border: #27272a;
  --border-light: #3f3f46;
  --text: #fafafa;
  --text-secondary: #a1a1aa;
  --text-muted: #71717a;
  --primary: #6366f1;
  --primary-light: #818cf8;
  --primary-dark: #4f46e5;
  --primary-glow: rgba(99,102,241,0.12);
  --accent: #06b6d4;
  --accent-light: #22d3ee;
  --success: #10b981;
  --warning: #f59e0b;
  --radius: 12px;
  --radius-lg: 20px;
  --radius-full: 9999px;
  --shadow: 0 4px 24px rgba(0,0,0,0.4);
  --shadow-lg: 0 12px 48px rgba(0,0,0,0.5);
  --transition: 0.25s cubic-bezier(0.4,0,0.2,1);
  --font: 'Inter',-apple-system,BlinkMacSystemFont,sans-serif;
  --font-mono: 'JetBrains Mono',monospace;
}

/* ===== Reset ===== */
*,*::before,*::after{margin:0;padding:0;box-sizing:border-box}
html{scroll-behavior:smooth}
body{font-family:var(--font);background:var(--bg);color:var(--text);line-height:1.7;overflow-x:hidden;-webkit-font-smoothing:antialiased}
a{color:var(--primary-light);text-decoration:none;transition:var(--transition)}
a:hover{color:var(--accent-light)}
img{max-width:100%;display:block}
.container{max-width:1200px;margin:0 auto;padding:0 1.5rem}
.container-narrow{max-width:800px}

/* ===== Navbar ===== */
.navbar{position:fixed;top:0;left:0;right:0;z-index:1000;background:rgba(9,9,11,0.85);backdrop-filter:blur(20px);border-bottom:1px solid var(--border);transition:var(--transition)}
.navbar.scrolled{background:rgba(9,9,11,0.97);box-shadow:var(--shadow)}
.nav-container{max-width:1200px;margin:0 auto;padding:0 1.5rem;display:flex;align-items:center;justify-content:space-between;height:70px}
.nav-logo{display:flex;align-items:center;gap:.75rem;text-decoration:none}
.logo-icon{width:40px;height:40px;border-radius:var(--radius);background:linear-gradient(135deg,var(--primary),var(--accent));display:flex;align-items:center;justify-content:center;font-size:1.1rem;color:#fff;flex-shrink:0}
.logo-title{font-weight:700;font-size:1.05rem;color:var(--text);display:block;line-height:1.2}
.logo-subtitle{font-size:.7rem;color:var(--text-secondary);display:block}
.nav-links{display:flex;gap:.25rem}
.nav-link{padding:.5rem 1rem;border-radius:var(--radius-full);color:var(--text-secondary);font-size:.9rem;font-weight:500;transition:var(--transition);display:flex;align-items:center;gap:.5rem;text-decoration:none}
.nav-link:hover,.nav-link.active{color:var(--text);background:var(--bg-tertiary)}
.nav-link.active{color:var(--primary-light);background:var(--primary-glow)}
.nav-cta{padding:.5rem 1.25rem;border-radius:var(--radius-full);background:var(--primary);color:#fff;font-weight:600;font-size:.85rem;display:flex;align-items:center;gap:.5rem;text-decoration:none;transition:var(--transition)}
.nav-cta:hover{background:var(--primary-dark);color:#fff;transform:translateY(-1px)}
.nav-actions{display:flex;align-items:center;gap:1rem}
.nav-toggle{display:none;background:none;border:none;cursor:pointer;padding:.5rem}
.nav-toggle span{display:block;width:22px;height:2px;background:var(--text);margin:5px 0;border-radius:2px;transition:var(--transition)}

.mobile-menu{display:none;position:fixed;top:70px;left:0;right:0;background:var(--bg-secondary);border-bottom:1px solid var(--border);padding:1rem;z-index:999;flex-direction:column;gap:.25rem}
.mobile-menu.open{display:flex;animation:fadeIn .3s ease}
.mobile-link{padding:.75rem 1rem;border-radius:var(--radius);color:var(--text-secondary);font-weight:500;display:flex;align-items:center;gap:.75rem;text-decoration:none;transition:var(--transition)}
.mobile-link:hover{background:var(--bg-tertiary);color:var(--text)}

@media(max-width:768px){
  .nav-links{display:none}
  .nav-toggle{display:block}
  .nav-cta{display:none}
  .logo-subtitle{display:none}
}

@keyframes fadeIn{from{opacity:0;transform:translateY(8px)}to{opacity:1;transform:translateY(0)}}

/* ===== Hero ===== */
.hero{min-height:100vh;padding:100px 0 60px;position:relative;overflow:hidden}
.hero-bg{position:absolute;top:0;left:0;right:0;bottom:0;z-index:0}
.hero-gradient{position:absolute;top:-20%;left:-5%;width:600px;height:600px;background:radial-gradient(circle,var(--primary-glow) 0%,transparent 70%);filter:blur(80px);animation:float 8s ease-in-out infinite}
@keyframes float{0%,100%{transform:translateY(0)}50%{transform:translateY(-30px)}}
.hero-inner{position:relative;z-index:1;display:grid;grid-template-columns:1.2fr .8fr;gap:3rem;align-items:center;min-height:calc(100vh - 160px)}
.hero-badge{display:inline-flex;align-items:center;gap:.5rem;padding:.4rem 1rem;border-radius:var(--radius-full);background:var(--primary-glow);border:1px solid rgba(99,102,241,0.3);color:var(--primary-light);font-size:.85rem;font-weight:500;margin-bottom:1.5rem}
.hero-title{font-size:clamp(2.2rem,5vw,3.5rem);font-weight:800;line-height:1.15;margin-bottom:1.5rem}
.text-gradient{background:linear-gradient(135deg,var(--primary-light),var(--accent-light));-webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text}
.hero-description{font-size:1.15rem;color:var(--text-secondary);max-width:540px;margin-bottom:2rem}
.hero-stats{display:flex;align-items:center;gap:1.5rem;margin-bottom:2rem;flex-wrap:wrap}
.stat-number{display:block;font-size:1.8rem;font-weight:800;color:var(--text)}
.stat-label{font-size:.8rem;color:var(--text-muted)}
.stat-divider{width:1px;height:40px;background:var(--border)}
.hero-actions{display:flex;gap:1rem;flex-wrap:wrap}
.hero-visual{display:flex;align-items:center;justify-content:center}
.hero-card{background:var(--bg-card);border:1px solid var(--border);border-radius:var(--radius-lg);overflow:hidden;width:100%;max-width:380px;box-shadow:var(--shadow-lg)}
.hero-card-header{padding:.75rem 1rem;border-bottom:1px solid var(--border);display:flex;gap:.5rem}
.dot{width:10px;height:10px;border-radius:50%}
.dot.red{background:#ef4444}.dot.yellow{background:#f59e0b}.dot.green{background:#10b981}
.hero-card-content{padding:1.5rem}
.subject-grid{display:grid;grid-template-columns:1fr 1fr;gap:1rem}
.subject-item{padding:1.25rem;border-radius:var(--radius);background:var(--bg-tertiary);border:1px solid var(--border);text-align:center;display:flex;flex-direction:column;align-items:center;gap:.5rem;transition:var(--transition)}
.subject-item i{font-size:1.5rem;color:var(--primary-light)}
.subject-item span{font-weight:600;font-size:.85rem}
.subject-item:hover{border-color:var(--primary);background:var(--primary-glow);transform:translateY(-2px)}

@media(max-width:768px){
  .hero-inner{grid-template-columns:1fr;text-align:center}
  .hero-description{margin-left:auto;margin-right:auto}
  .hero-stats{justify-content:center}
  .hero-actions{justify-content:center}
  .hero-visual{display:none}
}

/* ===== Buttons ===== */
.btn{display:inline-flex;align-items:center;gap:.5rem;padding:.65rem 1.5rem;border-radius:var(--radius-full);font-weight:600;font-size:.9rem;border:none;cursor:pointer;transition:var(--transition);text-decoration:none;white-space:nowrap;font-family:var(--font)}
.btn-lg{padding:.8rem 2rem;font-size:1rem}
.btn-sm{padding:.4rem 1rem;font-size:.8rem}
.btn-primary{background:var(--primary);color:#fff}
.btn-primary:hover{background:var(--primary-dark);color:#fff;transform:translateY(-2px);box-shadow:0 4px 20px rgba(99,102,241,0.4)}
.btn-outline{background:transparent;color:var(--text);border:1px solid var(--border)}
.btn-outline:hover{border-color:var(--primary);color:var(--primary-light);background:var(--primary-glow)}
.btn-white{background:#fff;color:var(--bg)}
.btn-white:hover{background:#f0f0f0;color:var(--bg);transform:translateY(-2px)}
.btn-outline-white{background:transparent;color:#fff;border:1px solid rgba(255,255,255,0.3)}
.btn-outline-white:hover{background:rgba(255,255,255,0.1);color:#fff}

/* ===== Sections ===== */
.section{padding:5rem 0}
.section-alt{background:var(--bg-secondary)}
.section-header{text-align:center;margin-bottom:3rem}
.section-badge{display:inline-block;padding:.3rem 1rem;border-radius:var(--radius-full);background:var(--primary-glow);border:1px solid rgba(99,102,241,0.2);color:var(--primary-light);font-size:.8rem;font-weight:600;text-transform:uppercase;letter-spacing:.05em;margin-bottom:1rem}
.section-title{font-size:clamp(1.8rem,3.5vw,2.5rem);font-weight:800;margin-bottom:.75rem}
.section-desc{color:var(--text-secondary);font-size:1.05rem;max-width:600px;margin:0 auto}
.section-footer{text-align:center;margin-top:2.5rem;display:flex;gap:1rem;justify-content:center;flex-wrap:wrap}

/* ===== Subject Cards ===== */
.subjects-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(260px,1fr));gap:1.5rem}
.subject-card{background:var(--bg-card);border:1px solid var(--border);border-radius:var(--radius-lg);padding:2rem;transition:var(--transition)}
.subject-card:hover{border-color:var(--primary);transform:translateY(-4px);box-shadow:var(--shadow-lg)}
.subject-card-icon{width:56px;height:56px;border-radius:var(--radius);display:flex;align-items:center;justify-content:center;font-size:1.4rem;margin-bottom:1.25rem}
.subject-card-icon.physics{background:rgba(99,102,241,0.15);color:#818cf8}
.subject-card-icon.chemistry{background:rgba(6,182,212,0.15);color:#22d3ee}
.subject-card-icon.maths{background:rgba(245,158,11,0.15);color:#fbbf24}
.subject-card-icon.biology{background:rgba(16,185,129,0.15);color:#34d399}
.subject-card h3{font-size:1.2rem;font-weight:700;margin-bottom:.5rem}
.subject-card p{color:var(--text-secondary);font-size:.9rem;margin-bottom:1rem}
.subject-classes{display:inline-block;padding:.25rem .75rem;border-radius:var(--radius-full);background:var(--bg-tertiary);font-size:.75rem;font-weight:600;color:var(--text-muted)}

/* ===== Notes ===== */
.note-card-expanded{background:var(--bg-card);border:1px solid var(--border);border-radius:var(--radius-lg);overflow:hidden;margin-bottom:1.5rem;transition:var(--transition)}
.note-card-expanded:hover{border-color:var(--primary)}
.note-header{padding:1.5rem 2rem;border-bottom:1px solid var(--border);display:flex;align-items:center;justify-content:space-between;flex-wrap:wrap;gap:.5rem}
.note-header h2{font-size:1.4rem;font-weight:700}
.note-header h2 a{color:var(--text);text-decoration:none}
.note-header h2 a:hover{color:var(--primary-light)}
.note-date{font-size:.8rem;color:var(--text-muted);display:flex;align-items:center;gap:.4rem}
.note-body{padding:2rem;position:relative}
.note-preview-content{max-height:400px;overflow:hidden}
.note-fade{position:absolute;bottom:0;left:0;right:0;height:120px;background:linear-gradient(transparent,var(--bg-card));pointer-events:none}
.note-footer{padding:1rem 2rem;border-top:1px solid var(--border)}

.note-list-item{display:flex;align-items:center;justify-content:space-between;padding:1.25rem 1.5rem;background:var(--bg-card);border:1px solid var(--border);border-radius:var(--radius);margin-bottom:.75rem;transition:var(--transition);cursor:pointer;text-decoration:none;color:var(--text)}
.note-list-item:hover{border-color:var(--primary);background:var(--bg-card-hover);transform:translateX(4px);color:var(--text)}
.note-list-item h3{font-size:1rem;font-weight:600;color:var(--text)}
.note-list-item .note-date{font-size:.8rem;flex-shrink:0}

.notes-grid{display:grid;gap:.75rem}

/* Notes filter */
.notes-filter{display:flex;gap:.5rem;margin-bottom:2rem;flex-wrap:wrap}
.filter-btn{padding:.45rem 1.2rem;border-radius:var(--radius-full);background:var(--bg-card);border:1px solid var(--border);color:var(--text-secondary);font-size:.85rem;font-weight:500;cursor:pointer;transition:var(--transition);font-family:var(--font)}
.filter-btn:hover,.filter-btn.active{background:var(--primary-glow);border-color:var(--primary);color:var(--primary-light)}

/* ===== Note Detail ===== */
.note-article{line-height:1.8}
.note-meta-hero{margin-top:.75rem;display:flex;gap:1rem;align-items:center;justify-content:center;flex-wrap:wrap;color:var(--text-secondary);font-size:.9rem}
.meta-tag{padding:.2rem .75rem;border-radius:var(--radius-full);background:var(--primary-glow);border:1px solid rgba(99,102,241,0.2);color:var(--primary-light);font-size:.8rem;font-weight:500}
.back-link{display:inline-flex;align-items:center;gap:.5rem;color:var(--text-secondary);font-weight:500;margin-bottom:.5rem;text-decoration:none;font-size:.9rem}
.back-link:hover{color:var(--primary-light)}
.note-nav{display:grid;grid-template-columns:1fr 1fr;gap:1rem;margin-top:3rem;padding-top:2rem;border-top:1px solid var(--border)}
.note-nav-link{padding:1.25rem;border:1px solid var(--border);border-radius:var(--radius);transition:var(--transition);text-decoration:none;color:var(--text)}
.note-nav-link:hover{border-color:var(--primary);background:var(--primary-glow);color:var(--text)}
.note-nav-link.next{text-align:right}
.note-nav-dir{font-size:.8rem;color:var(--text-muted);display:block;margin-bottom:.25rem}
.note-nav-title{font-weight:600;font-size:.95rem}

/* ===== Markdown Content ===== */
.markdown-content h1{font-size:1.8rem;font-weight:800;margin:2rem 0 1rem;border-bottom:1px solid var(--border);padding-bottom:.5rem}
.markdown-content h2{font-size:1.4rem;font-weight:700;margin:2rem 0 .75rem;color:var(--primary-light)}
.markdown-content h3{font-size:1.15rem;font-weight:600;margin:1.5rem 0 .5rem}
.markdown-content h4{font-size:1rem;font-weight:600;margin:1.25rem 0 .5rem;color:var(--accent-light)}
.markdown-content p{margin-bottom:1rem;color:var(--text-secondary)}
.markdown-content strong{color:var(--text);font-weight:600}
.markdown-content ul,.markdown-content ol{margin:.5rem 0 1rem 1.5rem;color:var(--text-secondary)}
.markdown-content li{margin-bottom:.35rem}
.markdown-content blockquote{border-left:3px solid var(--primary);padding:.75rem 1.25rem;margin:1.25rem 0;background:var(--primary-glow);border-radius:0 var(--radius) var(--radius) 0;color:var(--text-secondary)}
.markdown-content blockquote p{margin-bottom:0}
.markdown-content code{font-family:var(--font-mono);background:var(--bg-tertiary);padding:.15rem .45rem;border-radius:4px;font-size:.85em;color:var(--accent-light)}
.markdown-content pre{background:var(--bg-tertiary);border:1px solid var(--border);border-radius:var(--radius);padding:1.25rem;overflow-x:auto;margin:1.25rem 0}
.markdown-content pre code{background:none;padding:0;color:var(--text);font-size:.9rem}
.markdown-content table{width:100%;border-collapse:collapse;margin:1.25rem 0;font-size:.9rem}
.markdown-content th,.markdown-content td{border:1px solid var(--border);padding:.6rem 1rem;text-align:left}
.markdown-content th{background:var(--bg-tertiary);font-weight:600;color:var(--text)}
.markdown-content td{color:var(--text-secondary)}
.markdown-content hr{border:none;border-top:1px solid var(--border);margin:2.5rem 0}
.markdown-content img{border-radius:var(--radius);margin:1rem 0}
.markdown-content .katex-display{margin:1.5rem 0;overflow-x:auto;padding:.5rem 0}
.markdown-content .katex{font-size:1.1em}

/* ===== Reviews ===== */
.review-rating-big{display:inline-flex;align-items:center;gap:.3rem;color:#fbbf24;font-size:1.1rem}
.review-rating-big strong{color:var(--text);margin-left:.3rem;font-size:1.3rem}
.reviews-carousel{display:grid;grid-template-columns:repeat(auto-fit,minmax(300px,1fr));gap:1.5rem}
.reviews-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(300px,1fr));gap:1.25rem}
.review-card{background:var(--bg-card);border:1px solid var(--border);border-radius:var(--radius-lg);padding:1.5rem;transition:var(--transition)}
.review-card:hover{border-color:var(--primary);transform:translateY(-2px)}
.review-card-header{display:flex;align-items:center;gap:.75rem;margin-bottom:.75rem}
.review-avatar{width:42px;height:42px;border-radius:50%;background:linear-gradient(135deg,var(--primary),var(--accent));display:flex;align-items:center;justify-content:center;font-weight:700;color:#fff;font-size:1rem;flex-shrink:0}
.review-name{font-weight:600;font-size:.95rem}
.review-date{font-size:.75rem;color:var(--text-muted)}
.review-stars{color:#fbbf24;font-size:.85rem;margin-bottom:.5rem;letter-spacing:1px}
.review-text{color:var(--text-secondary);font-size:.9rem;line-height:1.6}

.reviews-summary{display:flex;gap:3rem;align-items:center;justify-content:center;padding:2.5rem;background:var(--bg-card);border:1px solid var(--border);border-radius:var(--radius-lg);margin-bottom:2.5rem;flex-wrap:wrap}
.reviews-summary-left{text-align:center}
.big-rating{font-size:4rem;font-weight:900;line-height:1;background:linear-gradient(135deg,#fbbf24,#f59e0b);-webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text}
.stars-row{color:#fbbf24;font-size:1.2rem;margin:.5rem 0}
.reviews-summary-right{flex:1;min-width:250px;max-width:400px}
.bar-row{display:flex;align-items:center;gap:.5rem;margin-bottom:.4rem;font-size:.85rem;color:var(--text-muted)}
.bar{flex:1;height:8px;background:var(--bg-tertiary);border-radius:4px;overflow:hidden}
.bar-fill{height:100%;background:linear-gradient(90deg,#fbbf24,#f59e0b);border-radius:4px}

/* ===== Contact ===== */
.contact-grid{display:grid;grid-template-columns:1fr 1fr;gap:2rem}
.contact-info-cards{display:flex;flex-direction:column;gap:1rem}
.contact-card{display:flex;align-items:flex-start;gap:1rem;padding:1.5rem;background:var(--bg-card);border:1px solid var(--border);border-radius:var(--radius-lg);transition:var(--transition)}
.contact-card:hover{border-color:var(--primary);transform:translateY(-2px)}
.contact-card-icon{width:48px;height:48px;border-radius:var(--radius);flex-shrink:0;background:var(--primary-glow);display:flex;align-items:center;justify-content:center;color:var(--primary-light);font-size:1.1rem}
.contact-card h3{font-weight:700;font-size:1rem;margin-bottom:.25rem}
.contact-card p{color:var(--text-secondary);font-size:.9rem;margin:0}
.contact-card a{color:var(--primary-light)}
.contact-map{min-height:400px;border-radius:var(--radius-lg);overflow:hidden;border:1px solid var(--border)}

@media(max-width:768px){
  .contact-grid{grid-template-columns:1fr}
  .contact-map{min-height:300px}
}

/* ===== Page Hero ===== */
.page-hero{padding:120px 0 50px;text-align:center;background:var(--bg-secondary);border-bottom:1px solid var(--border)}
.page-hero-sm{padding:110px 0 40px}
.page-hero h1{font-size:clamp(1.8rem,4vw,2.5rem);font-weight:800;margin-bottom:.5rem}
.page-hero h1 i{color:var(--primary-light)}
.page-hero p{color:var(--text-secondary);font-size:1.05rem}

/* ===== CTA ===== */
.cta-section{padding:3rem 0 5rem}
.cta-card{background:linear-gradient(135deg,var(--primary-dark),#7c3aed);border-radius:var(--radius-lg);padding:3.5rem;text-align:center;position:relative;overflow:hidden}
.cta-card::before{content:'';position:absolute;top:-50%;right:-20%;width:400px;height:400px;background:radial-gradient(circle,rgba(255,255,255,0.08),transparent 70%)}
.cta-content{position:relative;z-index:1}
.cta-content h2{font-size:clamp(1.5rem,3vw,2.2rem);font-weight:800;color:#fff;margin-bottom:1rem}
.cta-content p{color:rgba(255,255,255,0.8);font-size:1.05rem;max-width:500px;margin:0 auto 2rem}
.cta-actions{display:flex;gap:1rem;justify-content:center;flex-wrap:wrap}

/* ===== Footer ===== */
.footer{background:var(--bg-secondary);border-top:1px solid var(--border);padding:4rem 0 2rem}
.footer-grid{display:grid;grid-template-columns:1.5fr 1fr 1fr 1fr;gap:2rem;margin-bottom:3rem}
.footer-brand p{color:var(--text-secondary);margin-top:1rem;font-size:.9rem}
.footer-links h4{font-weight:700;margin-bottom:1rem;font-size:.95rem}
.footer-links a,.footer-links p{display:block;color:var(--text-secondary);font-size:.9rem;margin-bottom:.5rem;transition:var(--transition)}
.footer-links a:hover{color:var(--primary-light)}
.footer-links p i{color:var(--primary-light);margin-right:.4rem}
.footer-bottom{border-top:1px solid var(--border);padding-top:1.5rem;text-align:center;color:var(--text-muted);font-size:.85rem}

@media(max-width:768px){.footer-grid{grid-template-columns:1fr 1fr}}
@media(max-width:480px){.footer-grid{grid-template-columns:1fr}}

/* ===== Scrollbar ===== */
::-webkit-scrollbar{width:8px}
::-webkit-scrollbar-track{background:var(--bg)}
::-webkit-scrollbar-thumb{background:var(--border);border-radius:4px}
::-webkit-scrollbar-thumb:hover{background:var(--border-light)}

/* ===== Selection ===== */
::selection{background:var(--primary);color:#fff}