:root {
    --primary: #2563eb;
    --primary-dark: #1d4ed8;
    --bg: #f8fafc;
    --text: #0f172a;
    --text-light: #64748b;
    --card-bg: #ffffff;
    --border: #e2e8f0;
}

* { box-sizing: border-box; margin: 0; padding: 0; }

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--bg);
    color: var(--text);
    line-height: 1.6;
}

.container { max-width: 1100px; margin: 0 auto; padding: 0 20px; }
.flex-row { display: flex; justify-content: space-between; align-items: center; }

/* Navbar */
.navbar { background: #fff; border-bottom: 1px solid var(--border); padding: 15px 0; position: sticky; top: 0; z-index: 100; }
.logo { display: flex; align-items: center; gap: 10px; font-weight: 800; font-size: 1.5rem; color: var(--primary); text-decoration: none; }
.nav-links { display: flex; gap: 25px; align-items: center; }
.nav-links a { text-decoration: none; color: var(--text); font-weight: 500; font-size: 0.95rem; }
.btn-login { color: var(--primary) !important; border: 1px solid var(--primary); padding: 8px 18px; border-radius: 8px; }

/* Hero Section */
.hero-section { padding: 80px 0; text-align: center; }
h1 { font-size: 3rem; font-weight: 800; margin-bottom: 15px; color: #020617; }
.subtitle { font-size: 1.25rem; color: var(--text-light); max-width: 700px; margin: 0 auto 50px; }

/* Converter Card */
.converter-card {
    background: var(--card-bg);
    border-radius: 24px;
    padding: 30px;
    box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.1);
    border: 1px solid var(--border);
    max-width: 650px;
    margin: 0 auto;
}

.drop-zone {
    border: 2px dashed #cbd5e1;
    border-radius: 16px;
    padding: 50px 20px;
    cursor: pointer;
    background: #f1f5f9;
    transition: all 0.2s;
}

.drop-zone:hover { border-color: var(--primary); background: #eff6ff; }
.icon-upload { width: 64px; height: 64px; color: #94a3b8; margin-bottom: 15px; }

.file-list { margin-top: 20px; text-align: left; background: #f8fafc; border-radius: 12px; padding: 15px; }
.file-item { display: flex; justify-content: space-between; padding: 8px 0; border-bottom: 1px solid #edf2f7; font-size: 0.9rem; }
.file-item:last-child { border: none; }
.size { color: var(--text-light); }

.action-area { margin-top: 30px; display: flex; align-items: center; justify-content: center; gap: 20px; flex-wrap: wrap; }
.format-selector select { padding: 10px; border-radius: 8px; border: 1px solid var(--border); outline: none; }
.btn-primary { 
    background: var(--primary); color: white; border: none; padding: 14px 35px; 
    border-radius: 12px; font-weight: 600; cursor: pointer; font-size: 1rem;
    transition: background 0.2s;
}
.btn-primary:hover { background: var(--primary-dark); }

/* Features */
.grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); gap: 40px; margin-top: 60px; }
.feature-card { padding: 20px; }
.feature-card i { color: var(--primary); margin-bottom: 15px; width: 40px; height: 40px; }
.feature-card h3 { margin-bottom: 10px; }
.feature-card p { color: var(--text-light); font-size: 0.95rem; }

/* Status & Loading */
.processing-status { margin-top: 20px; }
.spinner { 
    width: 40px; height: 40px; border: 4px solid #f3f3f3; border-top: 4px solid var(--primary); 
    border-radius: 50%; animation: spin 1s linear infinite; margin: 0 auto 10px;
}
@keyframes spin { 0% { transform: rotate(0deg); } 100% { transform: rotate(360deg); } }

.footer { padding: 50px 0; text-align: center; color: var(--text-light); font-size: 0.85rem; border-top: 1px solid var(--border); margin-top: 80px; }