*,*::before,*::after{margin:0;padding:0;box-sizing:border-box;}html{scroll-behavior:smooth;-webkit-text-size-adjust:100%;overflow-x:hidden;}:root{--primary-color:#6366f1;--primary-dark:#4f46e5;--secondary-color:#8b5cf6;--accent-color:#ec4899;--bg-color:#f8fafc;--card-bg:#ffffff;--text-color:#1e293b;--text-light:#64748b;--border-color:#e2e8f0;--success-color:#10b981;--youtube-red:#ff0000;--shadow:0 4px 6px -1px rgba(0,0,0,0.1),0 2px 4px -1px rgba(0,0,0,0.06);--shadow-lg:0 10px 15px -3px rgba(0,0,0,0.1),0 4px 6px -2px rgba(0,0,0,0.05);}body{font-family:'Segoe UI',Tahoma,Geneva,Verdana,sans-serif;background:linear-gradient(135deg,#667eea 0%,#764ba2 100%);color:var(--text-color);line-height:1.6;min-height:100vh;padding:clamp(1rem,3vw,2rem)clamp(0.75rem,2vw,1rem);display:flex;flex-direction:column;align-items:center;}img,svg,iframe,video{max-width:100%;height:auto;display:block;}.back-btn{display:inline-flex;align-items:center;justify-content:center;gap:0.5rem;padding:0.75rem 1.25rem;background:var(--card-bg);color:var(--primary-color);text-decoration:none;border-radius:12px;font-weight:600;font-size:clamp(0.9rem,2.5vw,1rem);box-shadow:var(--shadow);transition:all 0.3s ease;margin-bottom:clamp(1.5rem,4vw,2rem);position:relative;overflow:hidden;border:2px solid transparent;width:fit-content;min-height:44px;}.back-btn::before{content:'';position:absolute;top:0;left:-100%;width:100%;height:100%;background:linear-gradient(90deg,transparent,rgba(99,102,241,0.1),transparent);transition:left 0.5s ease;}.back-btn:hover::before{left:100%;}.back-btn:hover{background:var(--primary-color);color:white;transform:translateX(-5px);box-shadow:var(--shadow-lg);border-color:var(--primary-color);}.back-btn:active{transform:translateX(-3px)scale(0.98);}.container{width:100%;max-width:800px;margin:0 auto;background:var(--card-bg);padding:clamp(1.5rem,4vw,2.5rem)clamp(1rem,3vw,2rem);border-radius:16px;box-shadow:var(--shadow-lg);animation:fadeInUp 0.6s ease;}.container h1{font-size:clamp(1.5rem,5vw,2rem);color:var(--primary-color);margin-bottom:0.75rem;text-align:center;line-height:1.3;}.container > p{font-size:clamp(0.95rem,2.5vw,1rem);color:var(--text-light);text-align:center;margin-bottom:clamp(1.5rem,4vw,2rem);line-height:1.7;}.input-box{display:flex;flex-direction:column;gap:1rem;margin-bottom:clamp(1.5rem,4vw,2rem);width:100%;}#ytLink{width:100%;padding:clamp(0.85rem,2.5vw,1rem)clamp(1rem,2.5vw,1.25rem);font-size:1rem;border:2px solid var(--border-color);border-radius:12px;transition:all 0.3s ease;background:var(--bg-color);min-height:48px;}#ytLink:focus{outline:none;border-color:var(--youtube-red);box-shadow:0 0 0 4px rgba(255,0,0,0.1);background:white;}#ytLink::placeholder{color:var(--text-light);}#fetchBtn{padding:clamp(1rem,2.5vw,1.25rem)clamp(1.5rem,3vw,2rem);background:linear-gradient(135deg,var(--primary-color)0%,var(--secondary-color)100%);color:white;border:none;border-radius:12px;font-size:clamp(0.95rem,2.5vw,1.05rem);font-weight:600;cursor:pointer;transition:all 0.3s ease;box-shadow:var(--shadow);position:relative;overflow:hidden;min-height:48px;width:100%;}#fetchBtn::before{content:'';position:absolute;top:0;left:-100%;width:100%;height:100%;background:linear-gradient(90deg,transparent,rgba(255,255,255,0.2),transparent);transition:left 0.5s ease;}#fetchBtn:hover::before{left:100%;}#fetchBtn:hover{transform:translateY(-3px);box-shadow:var(--shadow-lg);background:linear-gradient(135deg,var(--primary-dark)0%,var(--secondary-color)100%);}#fetchBtn:active{transform:translateY(-1px);}#fetchBtn:disabled{background:var(--text-light);cursor:not-allowed;box-shadow:none;}.thumbnail-preview{background:var(--bg-color);border:2px dashed var(--border-color);border-radius:12px;padding:clamp(1.5rem,4vw,2rem);min-height:200px;display:flex;align-items:center;justify-content:center;margin-bottom:clamp(1.5rem,4vw,2rem);position:relative;overflow:hidden;transition:all 0.3s ease;width:100%;}.thumbnail-preview:empty::after{content:'🖼️ Thumbnail will appear here';color:var(--text-light);font-size:clamp(1rem,2.5vw,1.1rem);font-weight:500;text-align:center;padding:1rem;}.thumbnail-preview img{max-width:100%;height:auto;border-radius:8px;box-shadow:var(--shadow-lg);transition:all 0.3s ease;animation:fadeIn 0.5s ease;object-fit:contain;}.thumbnail-preview:has(img){border-style:solid;border-color:var(--primary-color);padding:1rem;background:white;}.thumbnail-preview img:hover{transform:scale(1.02);box-shadow:0 15px 30px rgba(0,0,0,0.2);}.download-btn{display:inline-flex;align-items:center;justify-content:center;gap:0.5rem;padding:clamp(1rem,2.5vw,1.25rem)clamp(1.5rem,3vw,2.5rem);background:linear-gradient(135deg,var(--success-color)0%,#059669 100%);color:white;text-decoration:none;border-radius:12px;font-size:clamp(1rem,2.5vw,1.1rem);font-weight:600;box-shadow:var(--shadow);transition:all 0.3s ease;position:relative;overflow:hidden;width:100%;max-width:400px;margin:0 auto;min-height:48px;}.download-btn::before{content:'';position:absolute;top:0;left:-100%;width:100%;height:100%;background:linear-gradient(90deg,transparent,rgba(255,255,255,0.3),transparent);transition:left 0.5s ease;}.download-btn:hover::before{left:100%;}.download-btn:hover{transform:translateY(-3px)scale(1.02);box-shadow:var(--shadow-lg);background:linear-gradient(135deg,#059669 0%,#047857 100%);}.download-btn:active{transform:translateY(-1px)scale(1);}.download-btn.hidden{display:none;}@media(max-width:479px){body{padding:1rem 0.5rem;}.container{padding:1.25rem 0.75rem;border-radius:12px;}.back-btn{width:100%;margin-bottom:1rem;}.input-box{gap:0.75rem;margin-bottom:1.25rem;}#fetchBtn{width:100%;}.thumbnail-preview{min-height:150px;padding:1rem;}.download-btn{width:100%;max-width:100%;}}@media(min-width:640px){.container h1{font-size:clamp(1.75rem,4vw,2.25rem);}.input-box{flex-direction:row;gap:1rem;}#ytLink{flex:1;}#fetchBtn{white-space:nowrap;flex-shrink:0;width:auto;}.download-btn{width:auto;}}@media(min-width:768px){body{padding:clamp(2rem,4vw,3rem)clamp(1.5rem,3vw,2rem);}.container{padding:clamp(2rem,4vw,3rem)clamp(2rem,4vw,2.5rem);}.container h1{font-size:clamp(2rem,5vw,2.5rem);}.container > p{font-size:clamp(1rem,2.5vw,1.1rem);}.thumbnail-preview{padding:clamp(2rem,4vw,3rem);min-height:300px;}.thumbnail-preview:empty::after{font-size:clamp(1.1rem,2.5vw,1.25rem);}}@media(min-width:1024px){.container h1{font-size:clamp(2.25rem,4vw,3rem);}}@keyframes fadeInUp{from{opacity:0;transform:translateY(30px);}to{opacity:1;transform:translateY(0);}}@keyframes fadeIn{from{opacity:0;transform:scale(0.95);}to{opacity:1;transform:scale(1);}}*:focus{outline:2px solid var(--primary-color);outline-offset:2px;}@media(prefers-reduced-motion:reduce){*,*::before,*::after{animation-duration:0.01ms !important;animation-iteration-count:1 !important;transition-duration:0.01ms !important;}}