.loading-screen{position:fixed;top:0;left:0;width:100%;height:100%;background:linear-gradient(135deg,#000000 0%,#333333 100%);display:flex;align-items:center;justify-content:center;z-index:9999;transition:opacity 0.5s ease,visibility 0.5s ease;}.loading-screen.hidden{opacity:0;visibility:hidden;}.loading-spinner{width:40px;height:40px;border:3px solid rgba(255,255,255,0.3);border-top:3px solid white;border-radius:50%;animation:spin 1s linear infinite;}@keyframes spin{0%{transform:rotate(0deg);}100%{transform:rotate(360deg);}}.navbar{position:fixed;top:0;width:100%;background:rgba(255,255,255,0.95);backdrop-filter:blur(10px);border-bottom:1px solid rgba(0,0,0,0.1);z-index:1000;transition:all 0.3s ease;padding:1rem 0;}.navbar.scrolled{background:rgba(255,255,255,0.98);box-shadow:0 2px 20px rgba(0,0,0,0.1);padding:0.5rem 0;}.nav-container{display:flex;justify-content:space-between;align-items:center;}.navbar-brand{display:flex;align-items:center;font-weight:700;font-size:1.5rem;color:#2c3e50;text-decoration:none;}.brand-icon{font-size:2rem;margin-right:0.5rem;background:linear-gradient(135deg,#000000 0%,#333333 100%);-webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text;}.nav-links{display:flex;align-items:center;gap:2rem;}.nav-link{color:#666;text-decoration:none;font-weight:500;transition:color 0.3s ease;position:relative;}.nav-link:hover{color:#000000;}.nav-link::after{content:'';position:absolute;bottom:-5px;left:0;width:0;height:2px;background:linear-gradient(135deg,#000000 0%,#333333 100%);transition:width 0.3s ease;}.nav-link:hover::after{width:100%;}.mobile-menu-toggle{display:none;flex-direction:column;cursor:pointer;gap:4px;}.mobile-menu-toggle span{width:25px;height:3px;background:#333;transition:all 0.3s ease;}.hero-section{min-height:100vh;display:flex;align-items:center;position:relative;overflow:hidden;background:linear-gradient(135deg,#000000 0%,#333333 100%);padding-top:80px;}.hero-background{position:absolute;top:0;left:0;width:100%;height:100%;background:linear-gradient(135deg,#000000 0%,#333333 100%);}.hero-particles{position:absolute;width:100%;height:100%;background-image:radial-gradient(circle at 20% 80%,rgba(255,255,255,0.1) 1px,transparent 1px),radial-gradient(circle at 80% 20%,rgba(255,255,255,0.1) 1px,transparent 1px),radial-gradient(circle at 40% 40%,rgba(255,255,255,0.05) 1px,transparent 1px);background-size:100px 100px,150px 150px,200px 200px;animation:float 20s ease-in-out infinite;}@keyframes float{0%,100%{transform:translate(0,0);}33%{transform:translate(10px,-10px);}66%{transform:translate(-5px,15px);}}.hero-container{display:grid;grid-template-columns:1fr 1fr;gap:4rem;align-items:center;position:relative;z-index:2;}.hero-content{color:white;}.hero-title{font-size:4rem;font-weight:800;margin-bottom:1rem;line-height:1.1;display:flex;align-items:center;gap:1rem;color:white;}.hero-icon{font-size:5rem;background:linear-gradient(45deg,#fff,rgba(255,255,255,0.8));-webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text;}.hero-subtitle{font-size:1.5rem;font-weight:600;margin-bottom:1rem;opacity:0.9;color:white;}.hero-description{font-size:1.2rem;margin-bottom:2rem;opacity:0.95;line-height:1.6;font-weight:300;letter-spacing:0.5px;color:rgba(255,255,255,0.95);text-shadow:0 1px 2px rgba(0,0,0,0.1);}.hero-stats{display:flex;gap:2rem;margin-bottom:2rem;justify-content:center;}.stat-item{text-align:center;}.stat-number{display:block;font-size:2rem;font-weight:800;color:#fff;}.stat-label{font-size:0.9rem;opacity:0.8;color:white;}.hero-cta{margin-top:2rem;}.btn-hero{padding:1rem 2rem;font-size:1.2rem;font-weight:600;border-radius:12px;background:white;color:#000000;border:none;text-decoration:none;display:inline-flex;align-items:center;gap:0.5rem;transition:all 0.3s ease;box-shadow:0 4px 20px rgba(0,0,0,0.1);}.btn-hero:hover{transform:translateY(-2px);box-shadow:0 8px 30px rgba(0,0,0,0.2);color:#000000;}.btn-arrow{transition:transform 0.3s ease;}.btn-hero:hover .btn-arrow,.btn:hover .btn-arrow{transform:translateX(5px);}.cta-note{margin-top:1rem;opacity:0.7;font-size:0.9rem;}.hero-visual{display:flex;justify-content:center;align-items:center;}.floating-card{background:white;border-radius:16px;padding:2rem;box-shadow:0 20px 60px rgba(0,0,0,0.2);animation:floatCard 6s ease-in-out infinite;max-width:400px;}@keyframes floatCard{0%,100%{transform:translateY(0px);}50%{transform:translateY(-20px);}}.card-header{display:flex;justify-content:space-between;align-items:center;margin-bottom:1rem;padding-bottom:1rem;border-bottom:1px solid #eee;}.problem-type{font-weight:600;color:#333;}.difficulty-badge{padding:0.25rem 0.75rem;border-radius:20px;font-size:0.8rem;font-weight:600;color:white;}.difficulty-badge.olympiad{background:linear-gradient(135deg,#000000 0%,#333333 100%);}.problem-text{color:#666;margin-bottom:1rem;}.equation{font-family:'Computer Modern',serif;text-align:center;font-size:1.1rem;color:#333;}.fade-in-up{animation:fadeInUp 1s ease-out;}.fade-in-right{animation:fadeInRight 1s ease-out 0.3s both;}.slide-in-left{animation:slideInLeft 0.8s ease-out;}.slide-in-up{animation:slideInUp 0.8s ease-out 0.2s both;}.slide-in-right{animation:slideInRight 0.8s ease-out 0.4s both;}@keyframes fadeInUp{from{opacity:0;transform:translateY(30px);}to{opacity:1;transform:translateY(0);}}@keyframes fadeInRight{from{opacity:0;transform:translateX(30px);}to{opacity:1;transform:translateX(0);}}@keyframes slideInLeft{from{opacity:0;transform:translateX(-50px);}to{opacity:1;transform:translateX(0);}}@keyframes slideInUp{from{opacity:0;transform:translateY(50px);}to{opacity:1;transform:translateY(0);}}@keyframes slideInRight{from{opacity:0;transform:translateX(50px);}to{opacity:1;transform:translateX(0);}}.section-header{text-align:center;margin-bottom:4rem;}.section-title{font-size:3rem;font-weight:700;margin-bottom:1rem;color:#2c3e50;}.section-subtitle{font-size:1.2rem;color:#666;max-width:600px;margin:0 auto;}.features-section{padding:6rem 0;background:#f8fafc;}.features-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(300px,1fr));gap:3rem;}.feature-card{background:white;padding:3rem 2rem;border-radius:16px;box-shadow:0 4px 20px rgba(0,0,0,0.05);transition:all 0.3s ease;border:1px solid #f0f0f0;}.feature-card:hover{transform:translateY(-5px);box-shadow:0 10px 40px rgba(0,0,0,0.1);}.feature-icon-wrapper{margin-bottom:2rem;}.feature-icon{font-size:3rem;display:flex;align-items:center;justify-content:center;width:80px;height:80px;border-radius:20px;background:linear-gradient(135deg,#000000 0%,#333333 100%);margin:0 auto;color:white;}.feature-title{font-size:1.5rem;font-weight:600;margin-bottom:1rem;text-align:center;color:#2c3e50;}.feature-description{color:#666;margin-bottom:1.5rem;line-height:1.6;text-align:center;}.feature-list{list-style:none;padding:0;}.feature-list li{padding:0.5rem 0;color:#555;position:relative;padding-left:2rem;}.feature-list li::before{content:'✓';position:absolute;left:0;color:#000000;font-weight:bold;}.subjects-section{padding:6rem 0;}.subjects-tabs{max-width:1000px;margin:0 auto;}.tab-buttons{display:flex;justify-content:center;margin-bottom:3rem;border-bottom:1px solid #eee;}.tab-btn{padding:1rem 2rem;background:none;border:none;font-size:1.1rem;font-weight:500;color:#666;cursor:pointer;transition:all 0.3s ease;border-bottom:3px solid transparent;}.tab-btn.active{color:#000000;border-bottom-color:#000000;}.tab-btn:hover{color:#000000;}.tab-content{min-height:400px;}.tab-pane{display:none;animation:fadeInUp 0.5s ease-out;}.tab-pane.active{display:block;}.subjects-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(280px,1fr));gap:2rem;}.subject-card{background:white;padding:2rem;border-radius:12px;box-shadow:0 2px 10px rgba(0,0,0,0.05);transition:all 0.3s ease;border:1px solid #f0f0f0;text-align:center;}.subject-card:hover{transform:translateY(-3px);box-shadow:0 6px 25px rgba(0,0,0,0.1);}.subject-icon{font-size:2.5rem;margin-bottom:1rem;color:#000000;}.subject-card h4{font-size:1.3rem;font-weight:600;margin-bottom:1rem;color:#2c3e50;}.subject-card p{color:#666;line-height:1.6;}.pricing-section{padding:6rem 0;background:#f8fafc;}.pricing-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(300px,1fr));gap:2rem;max-width:1000px;margin:0 auto;}.pricing-card{background:white;border-radius:16px;padding:3rem 2rem;box-shadow:0 4px 20px rgba(0,0,0,0.05);transition:all 0.3s ease;position:relative;border:1px solid #f0f0f0;}.pricing-card.featured{border:2px solid #000000;transform:scale(1.05);}.pricing-card:hover{transform:translateY(-5px);box-shadow:0 10px 40px rgba(0,0,0,0.1);}.pricing-card.featured:hover{transform:scale(1.05) translateY(-5px);}.pricing-badge{position:absolute;top:-15px;left:50%;transform:translateX(-50%);background:linear-gradient(135deg,#000000 0%,#333333 100%);color:white;padding:0.5rem 1.5rem;border-radius:20px;font-size:0.9rem;font-weight:600;}.pricing-header{text-align:center;margin-bottom:2rem;}.pricing-title{font-size:1.5rem;font-weight:600;margin-bottom:1rem;color:#2c3e50;}.pricing-price{display:flex;align-items:baseline;justify-content:center;gap:0.25rem;}.price-amount{font-size:3rem;font-weight:700;color:#000000;}.price-period{color:#666;font-size:1.1rem;}.pricing-features ul{list-style:none;padding:0;margin-bottom:2rem;}.pricing-features li{padding:0.75rem 0;color:#555;position:relative;padding-left:2rem;}.feature-included::before{content:'✓';position:absolute;left:0;color:#22c55e;font-weight:bold;}.feature-excluded::before{content:'✗';position:absolute;left:0;color:#ef4444;font-weight:bold;}.pricing-btn{width:100%;padding:1rem;font-weight:600;border-radius:8px;text-decoration:none;text-align:center;transition:all 0.3s ease;justify-content:center;}.cta-section{padding:6rem 0;background:linear-gradient(135deg,#000000 0%,#333333 100%);color:white;text-align:center;}.cta-title{font-size:3rem;font-weight:700;margin-bottom:1rem;color:white;}.cta-subtitle{font-size:1.3rem;margin-bottom:3rem;opacity:0.9;max-width:800px;margin-left:auto;margin-right:auto;color:white;}.cta-buttons{display:flex;gap:1rem;justify-content:center;flex-wrap:wrap;margin-bottom:2rem;color:white;}.btn{display:inline-flex;align-items:center;gap:0.5rem;padding:1rem 2rem;font-size:1.1rem;font-weight:600;text-decoration:none;border-radius:8px;transition:all 0.3s ease;border:2px solid transparent;}.btn-primary{background:white;color:#000000;border-color:white;}.btn-primary:hover{background:#f5f5f5;color:#000000;transform:translateY(-2px);box-shadow:0 8px 25px rgba(255,255,255,0.3);}.btn-outline{background:transparent;color:white;border-color:white;}.btn-outline:hover{background:white;color:#000000;transform:translateY(-2px);box-shadow:0 8px 25px rgba(255,255,255,0.3);}.btn-lg{padding:1.25rem 2.5rem;font-size:1.2rem;}.cta-note{opacity:0.8;font-size:0.9rem;color:white;}.footer{background:#2c3e50;color:white;padding:4rem 0 2rem;}.footer-content{display:grid;grid-template-columns:1fr 2fr;gap:3rem;margin-bottom:3rem;}.footer-brand .brand{display:flex;align-items:center;margin-bottom:1rem;font-size:1.5rem;font-weight:700;}.footer-description{opacity:0.8;line-height:1.6;}.footer-links{display:grid;grid-template-columns:repeat(3,1fr);gap:2rem;}.footer-column h4{margin-bottom:1rem;font-weight:600;}.footer-column ul{list-style:none;padding:0;}.footer-column li{margin-bottom:0.5rem;}.footer-column a{color:rgba(255,255,255,0.8);text-decoration:none;transition:color 0.3s ease;}.footer-column a:hover{color:white;}.footer-bottom{text-align:center;padding-top:2rem;border-top:1px solid rgba(255,255,255,0.1);opacity:0.8;}@media (max-width:768px){.nav-links{display:none;}.mobile-menu-toggle{display:flex;}.hero-container{grid-template-columns:1fr;text-align:center;gap:2rem;}.hero-title{font-size:2.5rem;}.hero-stats{justify-content:center;}.section-title{font-size:2rem;}.features-grid,.subjects-grid,.pricing-grid{grid-template-columns:1fr;}.tab-buttons{flex-direction:column;align-items:center;}.cta-title{font-size:2rem;}.footer-content{grid-template-columns:1fr;text-align:center;}.footer-links{grid-template-columns:1fr;}}@media (max-width:480px){.hero-title{font-size:2rem;flex-direction:column;gap:0.5rem;}.hero-stats{flex-direction:column;gap:1rem;}.cta-buttons{flex-direction:column;align-items:center;}}