:root {
    --primary: #4f46e5;
    --primary-light: #eef2ff;
    --primary-hover: #4338ca;
    --bg-body: #f8f9fc;
    --bg-card: #ffffff;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.04);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.08);
    --radius: 12px;
    --radius-sm: 8px;
    --transition: all 0.2s ease;
}

* {
    box-sizing: border-box;
}

body {
    font-family: 'Inter', 'Noto Sans SC', -apple-system, BlinkMacSystemFont, sans-serif;
    background-color: var(--bg-body);
    color: var(--text-primary);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

main {
    flex: 1;
}

/* Navbar */
.navbar {
    box-shadow: var(--shadow-sm);
    padding: 0.75rem 0;
}

.navbar-brand {
    font-size: 1.2rem;
    color: var(--text-primary) !important;
}

.brand-icon {
    width: 36px;
    height: 36px;
    background: var(--primary);
    color: white;
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.1rem;
}

.nav-link {
    font-weight: 500;
    color: var(--text-secondary) !important;
    padding: 0.5rem 1rem !important;
    border-radius: var(--radius-sm);
    transition: var(--transition);
}

.nav-link:hover {
    color: var(--primary) !important;
    background: var(--primary-light);
}

.lang-btn {
    border-radius: 6px;
    font-weight: 500;
    font-size: 0.8rem;
    padding: 0.25rem 0.75rem;
}

.lang-btn.active {
    background: var(--primary);
    color: white;
    border-color: var(--primary);
}

/* Hero Section */
.hero-section {
    background: linear-gradient(135deg, #f8f9fc 0%, #eef2ff 100%);
    padding: 3rem 0 2rem;
}

.hero-title {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 0.75rem;
}

.hero-subtitle {
    font-size: 1.15rem;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto;
}

/* Section Titles */
.section-title {
    font-size: 1.3rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0;
    display: flex;
    align-items: center;
}

/* Tool Cards */
.tool-card-link {
    text-decoration: none;
    color: inherit;
    display: block;
    height: 100%;
}

.tool-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    padding: 1.5rem;
    height: 100%;
    transition: var(--transition);
    box-shadow: var(--shadow-sm);
}

.tool-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
    border-color: var(--primary);
}

.tool-icon {
    width: 48px;
    height: 48px;
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.4rem;
    margin-bottom: 1rem;
}

.tool-icon-lg {
    width: 64px;
    height: 64px;
    border-radius: var(--radius);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.8rem;
}

.tool-title {
    font-size: 1.05rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.tool-desc {
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin-bottom: 0;
    line-height: 1.5;
}

/* Tool Page */
.tool-page-header h1 {
    font-size: 1.75rem;
    font-weight: 700;
}

/* Upload Zone */
.upload-card {
    border-radius: var(--radius);
    overflow: hidden;
}

.upload-zone {
    border: 2px dashed var(--border-color);
    border-radius: var(--radius);
    padding: 3rem 2rem;
    text-align: center;
    transition: var(--transition);
    cursor: pointer;
    background: #fafbfd;
}

.upload-zone:hover,
.upload-zone.drag-over {
    border-color: var(--primary);
    background: var(--primary-light);
}

.upload-zone-content .upload-icon {
    font-size: 3rem;
    color: var(--text-secondary);
    margin-bottom: 1rem;
    display: block;
}

.upload-zone:hover .upload-icon,
.upload-zone.drag-over .upload-icon {
    color: var(--primary);
}

/* Buttons */
.btn-primary {
    background: var(--primary);
    border-color: var(--primary);
}

.btn-primary:hover {
    background: var(--primary-hover);
    border-color: var(--primary-hover);
}

/* Footer */
footer {
    background: var(--bg-card);
}

/* Responsive */
@media (max-width: 768px) {
    .hero-title {
        font-size: 1.75rem;
    }

    .hero-subtitle {
        font-size: 1rem;
    }

    .upload-zone {
        padding: 2rem 1rem;
    }

    .tool-card {
        padding: 1.25rem;
    }
}

/* Dropdown Menu */
.dropdown-menu {
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-md);
    border-radius: var(--radius-sm);
    padding: 0.5rem;
}

.dropdown-item {
    border-radius: 6px;
    padding: 0.5rem 1rem;
    font-size: 0.9rem;
    transition: var(--transition);
}

.dropdown-item:hover {
    background: var(--primary-light);
    color: var(--primary);
}

/* Form Controls */
.form-control:focus,
.form-select:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 0.2rem rgba(79, 70, 229, 0.15);
}

/* Alert */
.alert-success {
    background: #f0fdf4;
    color: #166534;
}

.alert-danger {
    background: #fef2f2;
    color: #991b1b;
}