*,*:before,*:after{box-sizing:border-box;margin:0;padding:0}:root{--primary: #2563eb;--primary-dark: #1d4ed8;--primary-light: #eff6ff;--accent: #10b981;--text: #1e293b;--text-muted: #64748b;--border: #e2e8f0;--bg: #ffffff;--bg-gray: #f8fafc;--radius: 12px;--shadow: 0 4px 24px rgba(0,0,0,.08)}html{scroll-behavior:smooth}body{font-family:Pretendard,-apple-system,BlinkMacSystemFont,Segoe UI,sans-serif;color:var(--text);background:var(--bg);line-height:1.6}a{text-decoration:none;color:inherit}img{max-width:100%;display:block}button{cursor:pointer;border:none;font-family:inherit}.nav{position:fixed;top:0;left:0;right:0;z-index:100;padding:16px 0;transition:all .3s}.nav.scrolled{background:#fffffff2;-webkit-backdrop-filter:blur(12px);backdrop-filter:blur(12px);box-shadow:0 1px 0 var(--border)}.nav-inner{max-width:1100px;margin:0 auto;padding:0 24px;display:flex;align-items:center;gap:32px}.nav-logo{font-size:1.4rem;font-weight:800;color:var(--primary)}.nav-links{display:flex;gap:28px;flex:1}.nav-links a{color:var(--text-muted);font-size:.95rem;font-weight:500;transition:color .2s}.nav-links a:hover{color:var(--primary)}.nav-actions{display:flex;gap:12px}.btn-primary{padding:9px 22px;background:var(--primary);color:#fff;border-radius:8px;font-size:.9rem;font-weight:600;transition:background .2s}.btn-primary:hover{background:var(--primary-dark)}.hero{position:relative;min-height:100vh;display:flex;align-items:center;padding:100px 24px 80px;overflow:hidden}.hero-bg{position:absolute;inset:0;z-index:-1;background:linear-gradient(135deg,#eff6ff,#ecfdf5,#f0f9ff)}.hero-bg:after{content:"";position:absolute;width:600px;height:600px;border-radius:50%;background:radial-gradient(circle,rgba(37,99,235,.08) 0%,transparent 70%);top:-100px;right:-100px}.hero-inner{max-width:680px;margin:0 auto;text-align:center}.hero-badge{display:inline-block;padding:6px 16px;background:#fff;border:1px solid var(--border);border-radius:999px;font-size:.875rem;color:var(--text-muted);margin-bottom:28px;box-shadow:0 1px 4px #0000000f}.hero-title{font-size:clamp(2.4rem,5vw,3.6rem);font-weight:800;line-height:1.2;margin-bottom:24px;color:var(--text)}.hero-title span{color:var(--primary)}.hero-desc{font-size:1.15rem;color:var(--text-muted);line-height:1.8;margin-bottom:40px}.hero-platforms{display:flex;gap:16px;justify-content:center;flex-wrap:wrap;max-width:780px;margin-inline:auto;margin-bottom:32px}.platform-card{display:flex;align-items:center;gap:14px;background:#fff;border:1px solid var(--border);border-radius:14px;padding:18px 20px;flex:1;min-width:200px;max-width:260px;text-align:left;transition:box-shadow .2s,transform .2s,border-color .2s;text-decoration:none;color:var(--text);box-shadow:0 2px 8px #0000000f}.platform-card:hover{transform:translateY(-3px);box-shadow:var(--shadow)}.platform-card.teacher:hover{border-color:var(--primary)}.platform-card.student:hover{border-color:var(--accent)}.platform-card.app{flex-direction:column;align-items:flex-start;cursor:default}.platform-card.app:hover{border-color:#8b5cf6}.platform-icon{font-size:1.8rem;flex-shrink:0}.platform-info{flex:1}.platform-info strong{display:block;font-size:.95rem;font-weight:700;margin-bottom:2px}.platform-info span{font-size:.78rem;color:var(--text-muted)}.platform-arrow{font-size:1.1rem;color:var(--text-muted);flex-shrink:0}.platform-card.app .platform-icon{font-size:1.6rem}.platform-card.app .platform-info{margin-bottom:12px}.platform-store-btns{display:flex;gap:8px;width:100%}.store-btn{flex:1;text-align:center;padding:7px 10px;background:var(--text);color:#fff;border-radius:7px;font-size:.75rem;font-weight:600;transition:opacity .2s}.store-btn:hover:not(.disabled){opacity:.8}.platform-card.disabled,.store-btn.disabled{opacity:.4;cursor:not-allowed;pointer-events:none}.hero-sub{display:flex;align-items:center;gap:12px;justify-content:center}.hero-link{font-size:.9rem;color:var(--text-muted);transition:color .2s}.hero-link:hover{color:var(--primary)}.hero-sub-dot{color:var(--border)}@media(max-width:640px){.platform-card{max-width:100%;min-width:unset}.hero-platforms{flex-direction:column;align-items:center}}.features{padding:100px 24px;background:var(--bg)}.section-inner{max-width:1100px;margin:0 auto}.section-header{text-align:center;margin-bottom:64px}.section-tag{display:inline-block;padding:5px 14px;background:var(--primary-light);color:var(--primary);border-radius:999px;font-size:.8rem;font-weight:600;margin-bottom:16px}.section-header h2{font-size:clamp(1.8rem,3vw,2.4rem);font-weight:800;margin-bottom:12px}.section-header p{color:var(--text-muted);font-size:1.05rem}.features-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(300px,1fr));gap:24px}.feature-card{padding:32px;border:1px solid var(--border);border-radius:var(--radius);background:#fff;transition:box-shadow .2s,transform .2s}.feature-card:hover{box-shadow:var(--shadow);transform:translateY(-4px)}.feature-icon{font-size:2rem;margin-bottom:16px}.feature-card h3{font-size:1.1rem;font-weight:700;margin-bottom:10px}.feature-card p{color:var(--text-muted);font-size:.92rem;line-height:1.7}.how{padding:100px 24px;background:var(--bg-gray)}.how-steps{display:flex;gap:0;align-items:flex-start;max-width:860px;margin:0 auto;position:relative}.how-step{flex:1;display:flex;flex-direction:column;align-items:center;position:relative}.how-step-number{width:56px;height:56px;border-radius:50%;background:var(--primary);color:#fff;display:flex;align-items:center;justify-content:center;font-size:1rem;font-weight:800;z-index:1;box-shadow:0 4px 14px #2563eb4d}.how-step-line{position:absolute;top:28px;left:50%;width:100%;height:2px;background:var(--border);z-index:0}.how-step-content{text-align:center;padding:20px 16px 0}.how-step-content h3{font-size:1.05rem;font-weight:700;margin-bottom:8px}.how-step-content p{color:var(--text-muted);font-size:.875rem;line-height:1.7}.contact{padding:100px 24px;background:#fff}.contact-layout{display:grid;grid-template-columns:1fr 1.2fr;gap:64px;align-items:start}@media(max-width:768px){.contact-layout{grid-template-columns:1fr}}.contact-info{padding-top:8px}.contact-info h2{font-size:clamp(1.8rem,3vw,2.2rem);font-weight:800;margin:16px 0}.contact-info p{color:var(--text-muted);line-height:1.8;margin-bottom:28px}.contact-list{list-style:none;display:flex;flex-direction:column;gap:12px}.contact-list li{color:var(--text);font-size:.95rem}.contact-form-wrap{background:var(--bg-gray);border-radius:20px;padding:40px}.contact-form{display:flex;flex-direction:column;gap:20px}.form-row{display:flex;flex-direction:column;gap:6px}.form-row label{font-size:.875rem;font-weight:600;color:var(--text)}.form-row label span{color:#ef4444}.form-row input,.form-row textarea,.form-row select{padding:12px 16px;border:1px solid var(--border);border-radius:8px;font-size:.95rem;font-family:inherit;background:#fff;transition:border-color .2s;resize:vertical}.form-row select{cursor:pointer}.form-row input:focus,.form-row textarea:focus,.form-row select:focus{outline:none;border-color:var(--primary);box-shadow:0 0 0 3px #2563eb1a}.form-error{color:#ef4444;font-size:.875rem}.form-submit{padding:14px;background:var(--primary);color:#fff;border-radius:10px;font-size:1rem;font-weight:700;transition:background .2s;margin-top:4px}.form-submit:hover:not(:disabled){background:var(--primary-dark)}.form-submit:disabled{opacity:.6;cursor:not-allowed}.contact-success{text-align:center;padding:32px 0}.contact-success-icon{font-size:3rem;margin-bottom:16px}.contact-success h3{font-size:1.3rem;font-weight:700;margin-bottom:8px}.contact-success p{color:var(--text-muted);margin-bottom:24px}.contact-success button{padding:10px 24px;background:var(--primary);color:#fff;border-radius:8px;font-size:.9rem;font-weight:600}.footer{background:#1e293b;color:#fff;padding:48px 24px 0}.footer-inner{max-width:1100px;margin:0 auto;display:flex;justify-content:space-between;align-items:flex-start;padding-bottom:40px;gap:32px;flex-wrap:wrap}.footer-logo{font-size:1.3rem;font-weight:800;color:#fff;margin-bottom:8px;display:block}.footer-brand p{color:#94a3b8;font-size:.875rem}.footer-links{display:flex;gap:24px;align-items:center;flex-wrap:wrap}.footer-links a{color:#94a3b8;font-size:.875rem;transition:color .2s}.footer-links a:hover{color:#fff}.footer-bottom{border-top:1px solid #334155;padding:20px 0;text-align:center;max-width:1100px;margin:0 auto}.footer-bottom p{color:#64748b;font-size:.8rem}.admin-login{min-height:100vh;display:flex;align-items:center;justify-content:center;background:var(--bg-gray)}.admin-login-card{background:#fff;border-radius:var(--radius);padding:48px 40px;box-shadow:var(--shadow);width:100%;max-width:400px;text-align:center}.admin-login-card h1{font-size:1.5rem;margin-bottom:8px}.admin-login-card p{color:var(--text-muted);margin-bottom:32px}.admin-login-card input{display:block;width:100%;padding:12px 16px;border:1px solid var(--border);border-radius:8px;font-size:1rem;margin-bottom:12px}.admin-login-card button{width:100%;padding:13px;background:var(--primary);color:#fff;border-radius:8px;font-size:1rem;font-weight:600;margin-top:8px}.admin-error{color:#ef4444;font-size:.875rem;margin-bottom:8px}.admin-layout{display:flex;min-height:100vh}.admin-sidebar{width:220px;background:#1e293b;color:#fff;display:flex;flex-direction:column;padding:24px 0;flex-shrink:0}.admin-logo{font-size:1.1rem;font-weight:700;padding:0 24px 24px;border-bottom:1px solid #334155}.admin-sidebar nav{flex:1;padding:16px 0}.admin-nav-item{display:flex;align-items:center;gap:8px;padding:10px 24px;width:100%;text-align:left;color:#94a3b8;font-size:.9rem;cursor:pointer;background:none;border:none;font-family:inherit}.admin-nav-item.active{background:#334155;color:#fff}.admin-badge{background:#ef4444;color:#fff;border-radius:999px;font-size:.75rem;padding:1px 7px;font-weight:600}.admin-logout{margin:0 16px;padding:10px;background:none;border:1px solid #334155;color:#94a3b8;border-radius:8px;font-size:.875rem;cursor:pointer}.admin-main{flex:1;display:flex;flex-direction:column;background:var(--bg-gray)}.admin-header{background:#fff;padding:20px 28px;border-bottom:1px solid var(--border);display:flex;align-items:center;gap:16px}.admin-header h2{font-size:1.25rem}.admin-count{color:var(--text-muted);font-size:.875rem}.admin-content{display:flex;flex:1;overflow:hidden}.admin-list{width:300px;border-right:1px solid var(--border);background:#fff;overflow-y:auto}.admin-item{display:block;width:100%;text-align:left;padding:16px 20px;border-bottom:1px solid var(--border);background:none;cursor:pointer;transition:background .15s}.admin-item:hover{background:var(--bg-gray)}.admin-item.active{background:var(--primary-light)}.admin-item.unread .admin-item-name{font-weight:700}.admin-item-top{display:flex;align-items:center;justify-content:space-between;margin-bottom:4px}.admin-item-name{font-size:.95rem}.admin-dot{width:8px;height:8px;background:var(--primary);border-radius:50%;flex-shrink:0}.admin-item-type{display:inline-block;font-size:.75rem;margin-bottom:2px;background:#eff6ff;color:var(--primary);border-radius:4px;padding:1px 6px;font-weight:500}.admin-item-date{font-size:.75rem;color:#94a3b8}.admin-detail{flex:1;padding:32px;overflow-y:auto}.admin-empty{color:var(--text-muted);text-align:center;padding:48px 0}.admin-detail-header{display:flex;justify-content:space-between;align-items:flex-start;margin-bottom:8px}.admin-detail-header h3{font-size:1.2rem;margin-bottom:4px}.admin-detail-email{color:var(--primary);font-size:.9rem}.admin-detail-type{display:inline-block;margin-left:8px;font-size:.8rem;background:#eff6ff;color:var(--primary);border-radius:4px;padding:2px 8px;font-weight:500}.admin-detail-date{font-size:.8rem;color:#94a3b8;margin-bottom:24px}.admin-detail-message{background:var(--bg-gray);border-radius:var(--radius);padding:20px;white-space:pre-wrap;line-height:1.8;margin-bottom:24px;font-size:.95rem}.admin-delete-btn{padding:8px 16px;background:#fff;border:1px solid #fca5a5;color:#ef4444;border-radius:8px;font-size:.875rem}.admin-reply-btn{display:inline-block;padding:12px 24px;background:var(--primary);color:#fff;border-radius:8px;font-weight:600}.admin-settings-wrap{flex:1;padding:40px;overflow-y:auto;background:var(--bg-gray);display:flex;flex-direction:column;gap:24px}.settings-section-title{font-size:1rem;font-weight:700;margin-bottom:24px;padding-bottom:12px;border-bottom:1px solid var(--border)}.admin-settings-form{background:#fff;border-radius:var(--radius);padding:36px 40px;max-width:560px;box-shadow:0 1px 4px #0000000f}.settings-group{margin-bottom:24px}.settings-group label{display:block;font-size:.875rem;font-weight:600;color:var(--text);margin-bottom:8px}.settings-group input{display:block;width:100%;padding:11px 14px;border:1px solid var(--border);border-radius:8px;font-size:.95rem;font-family:inherit;transition:border-color .15s}.settings-group input:focus{outline:none;border-color:var(--primary)}.settings-msg{font-size:.875rem;margin-bottom:16px;padding:10px 14px;border-radius:8px}.settings-msg.success{background:#f0fdf4;color:#16a34a}.settings-msg.error{background:#fef2f2;color:#dc2626}.settings-save-btn{padding:13px 32px;background:var(--primary);color:#fff;border-radius:8px;font-size:1rem;font-weight:600;transition:opacity .2s}.settings-save-btn:disabled{opacity:.6;cursor:not-allowed}