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

body {
    font-family: 'Inter', sans-serif;
    line-height: 1.6;
    transition: background 0.3s, color 0.3s;
}

.theme-light {
    --bg: #f8f9fa;
    --text: #1a1a2e;
    --card-bg: #ffffff;
    --shadow: 0 4px 15px rgba(0,0,0,0.08);
    --border: #e0e0e0;
    --primary: #6c63ff;
    --primary-hover: #5a52d5;
    --hero-bg: linear-gradient(135deg, #6c63ff 0%, #e2b0ff 100%);
    --footer-bg: #1a1a2e;
    --footer-text: #ffffff;
    --input-bg: #ffffff;
    --nav-bg: rgba(255,255,255,0.95);
    --nav-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

.theme-dark {
    --bg: #1a1a2e;
    --text: #e0e0e0;
    --card-bg: #16213e;
    --shadow: 0 4px 15px rgba(0,0,0,0.3);
    --border: #2a2a4a;
    --primary: #9b59b6;
    --primary-hover: #8e44ad;
    --hero-bg: linear-gradient(135deg, #1a1a2e 0%, #16213e 100%);
    --footer-bg: #0f0f23;
    --footer-text: #b0b0b0;
    --input-bg: #16213e;
    --nav-bg: rgba(22,33,62,0.95);
    --nav-shadow: 0 2px 10px rgba(0,0,0,0.3);
}

body {
    background: var(--bg);
    color: var(--text);
}

.header {
    position: fixed;
    top: 0;
    width: 100%;
    z-index: 1000;
    background: var(--nav-bg);
    box-shadow: var(--nav-shadow);
    backdrop-filter: blur(10px);
}

.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 2rem;
    max-width: 1200px;
    margin: 0 auto;
    height: 60px;
}

.nav-brand {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary);
}

.nav-links {
    display: flex;
    gap: 1.5rem;
    align-items: center;
}

.nav-links a {
    text-decoration: none;
    color: var(--text);
    font-weight: 500;
    transition: color 0.3s;
    font-size: 0.95rem;
}

.nav-links a:hover,
.nav-links a.active {
    color: var(--primary);
}

.nav-actions {
    display: flex;
    gap: 0.5rem;
    align-items: center;
}

.icon-btn {
    background: none;
    border: none;
    color: var(--text);
    font-size: 1.2rem;
    cursor: pointer;
    padding: 0.5rem;
    border-radius: 50%;
    transition: background 0.3s;
}

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

.hamburger {
    display: none;
    flex-direction: column;
    cursor: pointer;
    background: none;
    border: none;
    padding: 0.5rem;
}

.hamburger span {
    width: 25px;
    height: 3px;
    background: var(--text);
    margin: 3px 0;
    transition: 0.3s;
}

main {
    padding-top: 60px;
}

.hero {
    background: var(--hero-bg);
    padding: 5rem 2rem;
    text-align: center;
    color: #fff;
}

.hero h1 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
    font-weight: 700;
}

.hero p {
    font-size: 1.2rem;
    margin-bottom: 2rem;
    opacity: 0.9;
}

.btn-primary {
    display: inline-block;
    padding: 0.75rem 2rem;
    background: var(--primary);
    color: #fff;
    border: none;
    border-radius: 50px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    text-decoration: none;
    transition: background 0.3s, transform 0.2s;
}

.btn-primary:hover {
    background: var(--primary-hover);
    transform: translateY(-2px);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 2rem;
    padding: 4rem 2rem;
    max-width: 1200px;
    margin: 0 auto;
}

.feature-card {
    background: var(--card-bg);
    padding: 2rem;
    border-radius: 20px;
    box-shadow: var(--shadow);
    text-align: center;
    transition: transform 0.3s, box-shadow 0.3s;
}

.feature-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 25px rgba(0,0,0,0.15);
}

.feature-card i {
    font-size: 2.5rem;
    color: var(--primary);
    margin-bottom: 1rem;
}

.feature-card h3 {
    font-size: 1.3rem;
    margin-bottom: 0.5rem;
}

.feature-card p {
    font-size: 0.95rem;
    opacity: 0.8;
}

.footer {
    background: var(--footer-bg);
    color: var(--footer-text);
    text-align: center;
    padding: 2rem;
    margin-top: 2rem;
}

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

.footer a:hover {
    text-decoration: underline;
}

/* Chat page styles */
.chat-container {
    max-width: 800px;
    margin: 2rem auto;
    padding: 0 1rem;
}

.chat-box {
    background: var(--card-bg);
    border-radius: 20px;
    box-shadow: var(--shadow);
    padding: 1.5rem;
    min-height: 400px;
    max-height: 60vh;
    overflow-y: auto;
    margin-bottom: 1rem;
}

.chat-message {
    margin-bottom: 1rem;
    padding: 0.75rem 1rem;
    border-radius: 15px;
    max-width: 80%;
    animation: fadeIn 0.3s;
}

.chat-message.user {
    background: var(--primary);
    color: #fff;
    margin-left: auto;
    border-bottom-right-radius: 5px;
}

.chat-message.ai {
    background: var(--border);
    color: var(--text);
    margin-right: auto;
    border-bottom-left-radius: 5px;
}

.chat-message pre {
    background: #2d2d2d;
    padding: 1rem;
    border-radius: 10px;
    overflow-x: auto;
    margin: 0.5rem 0;
}

.chat-message code {
    font-family: 'Courier New', monospace;
    font-size: 0.9rem;
}

.chat-input-area {
    display: flex;
    gap: 0.5rem;
    align-items: center;
}

.chat-input-area input[type="text"] {
    flex: 1;
    padding: 0.75rem 1rem;
    border: 2px solid var(--border);
    border-radius: 50px;
    background: var(--input-bg);
    color: var(--text);
    font-size: 1rem;
    outline: none;
    transition: border-color 0.3s;
}

.chat-input-area input[type="text"]:focus {
    border-color: var(--primary);
}

.chat-input-area button {
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: 50px;
    background: var(--primary);
    color: #fff;
    cursor: pointer;
    font-size: 1rem;
    transition: background 0.3s;
}

.chat-input-area button:hover {
    background: var(--primary-hover);
}

.chat-input-area .icon-btn {
    font-size: 1.2rem;
    background: var(--border);
    border-radius: 50%;
    padding: 0.75rem;
}

.file-upload-area {
    margin-bottom: 1rem;
}

.file-upload-area input[type="file"] {
    display: none;
}

.file-upload-label {
    display: inline-block;
    padding: 0.5rem 1rem;
    background: var(--border);
    border-radius: 50px;
    cursor: pointer;
    transition: background 0.3s;
}

.file-upload-label:hover {
    background: var(--primary);
    color: #fff;
}

/* History page */
.history-list {
    max-width: 800px;
    margin: 2rem auto;
    padding: 0 1rem;
}

.history-item {
    background: var(--card-bg);
    padding: 1rem 1.5rem;
    border-radius: 15px;
    box-shadow: var(--shadow);
    margin-bottom: 1rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.history-item h4 {
    margin-bottom: 0.3rem;
}

.history-item p {
    font-size: 0.85rem;
    opacity: 0.7;
}

.history-item button {
    background: var(--primary);
    color: #fff;
    border: none;
    padding: 0.4rem 1rem;
    border-radius: 50px;
    cursor: pointer;
    transition: background 0.3s;
}

.history-item button:hover {
    background: var(--primary-hover);
}

/* Export page */
.export-container {
    max-width: 600px;
    margin: 2rem auto;
    padding: 0 1rem;
    text-align: center;
}

.export-btn {
    display: inline-block;
    margin: 0.5rem;
    padding: 0.75rem 2rem;
    background: var(--primary);
    color: #fff;
    border: none;
    border-radius: 50px;
    cursor: pointer;
    font-size: 1rem;
    transition: background 0.3s;
}

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

/* About page */
.about-section {
    max-width: 800px;
    margin: 2rem auto;
    padding: 2rem;
    background: var(--card-bg);
    border-radius: 20px;
    box-shadow: var(--shadow);
}

.about-section h2 {
    margin-bottom: 1rem;
    color: var(--primary);
}

/* Admin page */
.admin-section {
    max-width: 800px;
    margin: 2rem auto;
    padding: 0 1rem;
}

.login-form {
    background: var(--card-bg);
    padding: 2rem;
    border-radius: 20px;
    box-shadow: var(--shadow);
    max-width: 400px;
    margin: 0 auto;
}

.login-form h2 {
    margin-bottom: 1rem;
    text-align: center;
}

.login-form input {
    width: 100%;
    padding: 0.75rem;
    margin-bottom: 1rem;
    border: 2px solid var(--border);
    border-radius: 10px;
    background: var(--input-bg);
    color: var(--text);
}

.admin-panel {
    background: var(--card-bg);
    padding: 2rem;
    border-radius: 20px;
    box-shadow: var(--shadow);
}

.admin-panel textarea {
    margin-bottom: 1rem;
    border: 2px solid var(--border);
    border-radius: 10px;
    background: var(--input-bg);
    color: var(--text);
    padding: 1rem;
}

.error-msg {
    color: #e74c3c;
    margin-bottom: 1rem;
}

.success-msg {
    color: #2ecc71;
    margin-bottom: 1rem;
}

/* Features page */
.features-page {
    max-width: 1200px;
    margin: 2rem auto;
    padding: 0 2rem;
}

.features-page h2 {
    text-align: center;
    margin-bottom: 2rem;
    color: var(--primary);
}

/* Responsive */
@media (max-width: 768px) {
    .nav-links {
        display: none;
        flex-direction: column;
        position: absolute;
        top: 60px;
        left: 0;
        width: 100%;
        background: var(--nav-bg);
        padding: 1rem 0;
        box-shadow: var(--nav-shadow);
    }

    .nav-links.active {
        display: flex;
    }

    .hamburger {
        display: flex;
    }

    .hero h1 {
        font-size: 1.8rem;
    }

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

    .features-grid {
        grid-template-columns: 1fr;
        padding: 2rem 1rem;
    }

    .chat-message {
        max-width: 90%;
    }
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}