:root {
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --secondary-color: #f8fafc;
    --text-main: #0f172a;
    --text-muted: #64748b;
    --border-color: #e2e8f0;
    --danger-color: #ef4444;
    --success-color: #22c55e;
    --bg-color: #ffffff;
    --card-bg: #ffffff;
    --radius-md: 12px;
    --radius-lg: 16px;
    --shadow-sm: 0 1px 3px rgba(0,0,0,0.1);
    --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.1), 0 2px 4px -1px rgba(0,0,0,0.06);
    --shadow-hover: 0 10px 15px -3px rgba(0,0,0,0.1), 0 4px 6px -2px rgba(0,0,0,0.05);
    --transition: all 0.2s ease-in-out;
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    background-color: var(--secondary-color);
    color: var(--text-main);
    line-height: 1.6;
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Header */
header {
    background-color: var(--bg-color);
    box-shadow: var(--shadow-sm);
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-inner {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
    text-decoration: none;
    display: flex;
    align-items: center;
    gap: 8px;
}

nav ul {
    list-style: none;
    display: flex;
    gap: 24px;
}

nav a {
    text-decoration: none;
    color: var(--text-main);
    font-weight: 500;
    transition: var(--transition);
}

nav a:hover {
    color: var(--primary-color);
}

/* Hero Section */
.hero {
    text-align: center;
    padding: 4rem 20px;
    background: linear-gradient(135deg, var(--bg-color) 0%, var(--secondary-color) 100%);
}

.hero h1 {
    font-size: 3rem;
    margin-bottom: 1rem;
    font-weight: 800;
    letter-spacing: -0.025em;
}

.hero p {
    font-size: 1.25rem;
    color: var(--text-muted);
    max-width: 600px;
    margin: 0 auto 2rem;
}

/* Grid Layouts */
.tools-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 24px;
    padding: 40px 0;
}

/* Tool Card */
.tool-card {
    background: var(--card-bg);
    border-radius: var(--radius-lg);
    padding: 24px;
    text-decoration: none;
    color: var(--text-main);
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.tool-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-hover);
    border-color: var(--primary-color);
}

.tool-icon {
    width: 48px;
    height: 48px;
    background-color: #eff6ff;
    color: var(--primary-color);
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 24px;
}

.tool-card h3 {
    font-size: 1.25rem;
    font-weight: 600;
}

.tool-card p {
    color: var(--text-muted);
    font-size: 0.95rem;
}

/* Upload Box */
.upload-area {
    border: 2px dashed var(--border-color);
    border-radius: var(--radius-lg);
    padding: 3rem 2rem;
    text-align: center;
    background-color: var(--bg-color);
    transition: var(--transition);
    cursor: pointer;
    margin: 2rem auto;
    max-width: 800px;
}

.upload-area:hover, .upload-area.dragover {
    border-color: var(--primary-color);
    background-color: #f8fafc;
}

.upload-icon {
    font-size: 48px;
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.btn {
    display: inline-block;
    background-color: var(--primary-color);
    color: white;
    padding: 12px 24px;
    border-radius: var(--radius-md);
    text-decoration: none;
    font-weight: 600;
    border: none;
    cursor: pointer;
    transition: var(--transition);
    font-size: 1rem;
}

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

.btn:disabled {
    background-color: var(--text-muted);
    cursor: not-allowed;
}

/* Ad Blocks */
.ad-slot {
    background: #f1f5f9;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 20px;
    text-align: center;
    color: var(--text-muted);
    margin: 24px 0;
    font-size: 0.85rem;
}

/* Footer */
footer {
    margin-top: auto;
    background: var(--bg-color);
    border-top: 1px solid var(--border-color);
    padding: 2rem 0;
    text-align: center;
    color: var(--text-muted);
}

.footer-links {
    margin-top: 1rem;
    display: flex;
    justify-content: center;
    gap: 1rem;
}

.footer-links a {
    color: var(--text-muted);
    text-decoration: none;
}

.footer-links a:hover {
    color: var(--primary-color);
}

/* Responsive */
@media (max-width: 768px) {
    .tools-grid { grid-template-columns: 1fr; }
    .hero h1 { font-size: 2rem; }
}