:root{--primary: #6366f1;--primary-hover: #4f46e5;--bg-dark: #0f172a;--bg-card: #1e293b;--text-main: #f8fafc;--text-muted: #94a3b8;--accent: #818cf8;--success: #10b981;--error: #ef4444;--border: #334155;--glass: rgba(30, 41, 59, .7);--glass-border: rgba(255, 255, 255, .1);--header-height: 72px;--nav-merge: #fbbf24;--nav-split: #60a5fa;--header-shadow: 0 4px 6px -1px rgba(0, 0, 0, .3), 0 2px 4px -1px rgba(0, 0, 0, .06);--footer-shadow: 0 -4px 6px -1px rgba(0, 0, 0, .3), 0 -2px 4px -1px rgba(0, 0, 0, .06)}*{margin:0;padding:0;box-sizing:border-box}body{font-family:Inter,-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,sans-serif;background-color:var(--bg-dark);color:var(--text-main);line-height:1.5;overflow-x:hidden;padding-top:var(--header-height)}#root{height:100vh;display:flex;flex-direction:column}.premium-bg{position:fixed;top:0;left:0;width:100%;height:100%;z-index:-1;background:radial-gradient(circle at 0% 0%,rgba(99,102,241,.15) 0%,transparent 50%),radial-gradient(circle at 100% 100%,rgba(129,140,248,.1) 0%,transparent 50%)}.container{max-width:1200px;margin:0 auto;padding:2rem;width:100%}.glass-card{background:var(--glass);-webkit-backdrop-filter:blur(12px);backdrop-filter:blur(12px);border:1px solid var(--glass-border);border-radius:1.5rem;padding:2rem;box-shadow:0 25px 50px -12px #00000080}h1{font-size:3rem;font-weight:800;background:linear-gradient(to right,#6366f1,#a855f7);-webkit-background-clip:text;background-clip:text;-webkit-text-fill-color:transparent;margin-bottom:1rem;letter-spacing:-.025em}p{color:var(--text-muted);font-size:1.125rem}button{cursor:pointer;transition:all .2s ease;font-family:inherit}.btn-primary{background:var(--primary);color:#fff;border:none;padding:.75rem 1.5rem;border-radius:.75rem;font-weight:600;display:flex;align-items:center;gap:.5rem}.btn-primary:hover{background:var(--primary-hover);transform:translateY(-2px);box-shadow:0 10px 15px -3px #6366f166}.btn-primary:disabled{opacity:.5;cursor:not-allowed;transform:none}.fixed-header{position:fixed;top:0;left:0;width:100%;height:var(--header-height);background:#0f172acc;backdrop-filter:blur(12px);-webkit-backdrop-filter:blur(12px);box-shadow:var(--header-shadow);z-index:1000;display:flex;align-items:center;border-bottom:1px solid var(--glass-border)}.header-content{max-width:1200px;margin:0 auto;width:100%;padding:0 2rem;display:flex;justify-content:space-between;align-items:center}.logo{display:flex;align-items:center;gap:.75rem;cursor:pointer;text-decoration:none;color:inherit}.logo-icon{width:40px;height:40px;display:flex;align-items:center;justify-content:center;overflow:hidden}.logo-text{font-weight:800;font-size:1.25rem;letter-spacing:-.025em}.nav-links{display:flex;gap:2rem;align-items:center}.nav-item{font-weight:600;font-size:.95rem;cursor:pointer;transition:all .2s;display:flex;align-items:center;gap:.5rem;position:relative;padding:.5rem 0}.nav-item:hover{opacity:.8}.nav-item.active:after{content:"";position:absolute;bottom:-2px;left:0;width:100%;height:2px;background:currentColor;border-radius:2px}.nav-merge{color:var(--nav-merge)}.nav-split{color:var(--nav-split)}.help-btn{background:#ffffff0d;width:36px;height:36px;border-radius:50%;display:flex;align-items:center;justify-content:center;border:1px solid var(--glass-border);transition:all .2s}.help-btn:hover{background:#ffffff1a;transform:scale(1.05)}.modern-footer{margin-top:auto;background:#0f172a66;backdrop-filter:blur(8px);-webkit-backdrop-filter:blur(8px);border-top:1px solid var(--glass-border);box-shadow:var(--footer-shadow);padding:3rem 0}.footer-content{max-width:1200px;margin:0 auto;padding:0 2rem;display:grid;grid-template-columns:repeat(auto-fit,minmax(200px,1fr));gap:3rem}.footer-brand h4{font-size:1.25rem;margin-bottom:1rem;background:linear-gradient(to right,#6366f1,#a855f7);-webkit-background-clip:text;background-clip:text;-webkit-text-fill-color:transparent}.footer-links h5{color:var(--text-main);font-size:.9rem;text-transform:uppercase;letter-spacing:.05em;margin-bottom:1.25rem}.footer-links ul{list-style:none}.footer-links li{margin-bottom:.75rem}.footer-links a{color:var(--text-muted);text-decoration:none;font-size:.9rem;transition:color .2s}.footer-links a:hover{color:var(--primary)}.footer-bottom{max-width:1200px;margin:3rem auto 0;padding:2rem 2rem 0;border-top:1px solid var(--glass-border);text-align:center;color:var(--text-muted);font-size:.85rem}.tool-container{margin-top:0}.upload-area{border:2px dashed var(--border);border-radius:1rem;padding:3rem;text-align:center;transition:all .2s;cursor:pointer;margin-bottom:2rem}.upload-area.merge:hover{border-color:var(--nav-merge);background:#fbbf2405}.upload-area.split:hover{border-color:var(--nav-split);background:#60a5fa05}.file-list,.file-display{display:flex;flex-direction:column;gap:.75rem;margin-bottom:2rem}.file-item,.file-display-item{display:flex;justify-content:space-between;align-items:center;background:#ffffff0d;padding:.75rem 1rem;border-radius:.75rem;border:1px solid var(--border)}.remove-btn{background:transparent;border:none;color:var(--text-muted);font-size:1.25rem;padding:.25rem .5rem;cursor:pointer;transition:color .1s}.remove-btn:hover{color:var(--error)}.error-message{color:var(--error);background:#ef44441a;padding:1rem;border-radius:.75rem;margin-bottom:1.5rem;border:1px solid rgba(239,68,68,.2)}.loader{width:20px;height:20px;border:3px solid rgba(255,255,255,.3);border-radius:50%;border-top-color:#fff;animation:spin 1s ease-in-out infinite}@keyframes spin{to{transform:rotate(360deg)}}