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

:root {
    --bg-primary: #fafafa;
    --bg-secondary: #f5f5f5;
    --bg-tertiary: #efefef;
    --text-primary: #111111;
    --text-secondary: #555555;
    --text-tertiary: #888888;
    --border-color: #e0e0e0;
    --accent: #3366ff;
    --accent-light: #f0f4ff;
    --error: #ff3333;
    --success: #00cc66;
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.04);
    --shadow-md: 0 2px 8px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.1);
}

body.dark {
    --bg-primary: #0a0a0a;
    --bg-secondary: #121212;
    --bg-tertiary: #1a1a1a;
    --text-primary: #ffffff;
    --text-secondary: #e0e0e0;
    --text-tertiary: #b0b0b0;
    --border-color: #2a2a2a;
    --accent-light: rgba(51, 102, 255, 0.12);
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 12px 32px rgba(0, 0, 0, 0.5);
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Helvetica Neue', sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.5;
    transition: background 0.3s ease, color 0.3s ease;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    font-weight: 400;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

.app {
    flex: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 40px 20px;
}

.container {
    width: 100%;
    max-width: 1200px;
}

/* Theme Toggle */
.theme-btn {
    position: fixed;
    top: 24px;
    right: 24px;
    z-index: 100;
    width: 40px;
    height: 40px;
    border-radius: 10px;
    border: 1px solid var(--border-color);
    background: var(--bg-secondary);
    color: var(--text-primary);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 16px;
    transition: all 0.2s ease;
}

.theme-btn:hover {
    background: var(--bg-tertiary);
    transform: scale(1.05);
}

/* Header */
.header-section {
    text-align: center;
    margin-bottom: 60px;
}

.header-section h1 {
    font-size: 48px;
    font-weight: 600;
    margin-bottom: 6px;
    letter-spacing: -0.5px;
}

.header-section p {
    font-size: 14px;
    color: var(--text-tertiary);
    font-weight: 400;
    letter-spacing: 0.3px;
}

/* Main Grid */
.main-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 60px;
    align-items: start;
}

/* Control Panel */
.control-panel {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.input-group {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.url-input {
    padding: 12px 14px;
    border: 1px solid var(--border-color);
    border-radius: 6px;
    background: var(--bg-secondary);
    color: var(--text-primary);
    font-size: 13px;
    font-family: inherit;
    transition: all 0.2s ease;
    font-weight: 400;
}

.url-input:focus {
    outline: none;
    border-color: var(--accent);
    background: var(--accent-light);
    color: var(--text-primary);
}

.url-input::placeholder {
    color: var(--text-tertiary);
}

/* Buttons */
.btn-generate {
    padding: 12px 18px;
    background: var(--accent);
    color: white;
    border: none;
    border-radius: 6px;
    font-size: 13px;
    font-weight: 600;
    letter-spacing: 0.2px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    transition: all 0.2s ease;
    font-family: inherit;
}

.btn-generate:hover {
    background: #0052cc;
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.btn-generate:active {
    transform: translateY(0);
}

.btn-secondary {
    padding: 10px 14px;
    background: var(--bg-secondary);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
    border-radius: 6px;
    font-size: 13px;
    font-weight: 600;
    letter-spacing: 0.2px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 6px;
    transition: all 0.2s ease;
    font-family: inherit;
}

.btn-secondary:hover {
    background: var(--bg-tertiary);
    border-color: var(--accent);
    color: var(--accent);
}

.btn-download {
    padding: 10px 14px;
    background: transparent;
    color: var(--text-primary);
    border: 1px solid var(--border-color);
    border-radius: 6px;
    font-size: 12px;
    font-weight: 600;
    letter-spacing: 0.2px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 6px;
    transition: all 0.2s ease;
    font-family: inherit;
}

.btn-download:hover:not(:disabled) {
    border-color: var(--accent);
    color: var(--accent);
    background: var(--accent-light);
}

.btn-download:disabled {
    opacity: 0.4;
    cursor: not-allowed;
}

.btn-primary {
    padding: 12px 16px;
    background: var(--accent);
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    transition: all 0.2s ease;
    font-family: inherit;
}

.btn-primary:hover {
    background: #0052cc;
}

/* Divider */
.divider {
    height: 1px;
    background: var(--border-color);
}

/* Customize Section */
.customize-section {
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.customize-section h3 {
    font-size: 12px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.8px;
    color: var(--text-tertiary);
}

.control-group {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.control-group label {
    font-size: 12px;
    font-weight: 600;
    letter-spacing: 0.3px;
    color: var(--text-tertiary);
}

/* Color Grid */
.color-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 12px;
}

.color-input {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.color-input input {
    width: 100%;
    height: 70px;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.2s ease;
}

.color-input input:hover {
    border-color: var(--accent);
}

.color-input span {
    font-size: 11px;
    color: var(--text-tertiary);
    font-family: 'Courier New', monospace;
    font-weight: 600;
}

/* Level Buttons */
.level-buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 8px;
}

.level-btn {
    padding: 9px;
    background: var(--bg-secondary);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
    border-radius: 5px;
    font-size: 12px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
    font-family: inherit;
    letter-spacing: 0.2px;
}

.level-btn:hover {
    border-color: var(--accent);
    background: var(--accent-light);
    color: var(--accent);
}

.level-btn.active {
    background: var(--accent);
    color: white;
    border-color: var(--accent);
}

/* Preview Panel */
.preview-panel {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.qr-wrapper {
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 32px;
    background: var(--bg-secondary);
    border-radius: 10px;
    min-height: 380px;
}

.qr-display {
    width: 100%;
    max-width: 320px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: white;
    border-radius: 8px;
    aspect-ratio: 1;
}

body.dark .qr-display {
    background: #1a1a1a;
}

.qr-placeholder {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 12px;
    color: var(--text-tertiary);
    text-align: center;
}

.qr-placeholder i {
    font-size: 48px;
    opacity: 0.3;
}

.qr-placeholder p {
    font-size: 13px;
}

/* URL Info */
.url-info {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.url-info .label {
    font-size: 12px;
    font-weight: 600;
    color: var(--text-tertiary);
    text-transform: uppercase;
    letter-spacing: 0.8px;
}

.url-text {
    font-size: 12px;
    color: var(--text-secondary);
    word-break: break-all;
    font-family: 'Courier New', monospace;
    font-weight: 400;
    letter-spacing: 0.1px;
}

/* Action Buttons */
.action-buttons {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 12px;
}

/* Modal */
.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.5);
    z-index: 1000;
    align-items: center;
    justify-content: center;
    padding: 20px;
}

.modal.show {
    display: flex;
}

.modal-content {
    background: var(--bg-primary);
    border-radius: 12px;
    padding: 32px;
    max-width: 500px;
    width: 100%;
    box-shadow: var(--shadow-lg);
    animation: slideUp 0.3s ease;
    position: relative;
}

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.modal-content h2 {
    font-size: 20px;
    margin-bottom: 20px;
    font-weight: 600;
}

.modal-close {
    position: absolute;
    top: 16px;
    right: 16px;
    width: 32px;
    height: 32px;
    border: none;
    background: var(--border-color);
    border-radius: 6px;
    color: var(--text-primary);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s ease;
    font-size: 16px;
    z-index: 10;
}

.modal-close:hover {
    background: var(--accent);
    color: white;
    transform: scale(1.1);
}

.modal-actions {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 12px;
    margin-top: 20px;
}

/* Footer */
.footer {
    text-align: center;
    padding: 40px 20px;
    border-top: 1px solid var(--border-color);
    color: var(--text-tertiary);
    font-size: 12px;
    margin-top: auto;
}

.footer-content {
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 16px;
}

.footer-text {
    color: var(--text-tertiary);
    font-size: 12px;
    margin: 0;
}

.footer-links {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 20px;
}

.footer-links a {
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 6px;
    background: var(--bg-secondary);
    color: var(--text-secondary);
    text-decoration: none;
    transition: all 0.2s ease;
    font-size: 14px;
}

.footer-links a:hover {
    background: var(--accent);
    color: white;
    transform: translateY(-2px);
}

/* Responsive */
@media (max-width: 1024px) {
    .main-grid {
        grid-template-columns: 1fr;
        gap: 50px;
    }

    .header-section h1 {
        font-size: 40px;
    }

    .qr-wrapper {
        min-height: 400px;
    }
}

@media (max-width: 640px) {
    .app {
        padding: 30px 16px;
    }

    .container {
        padding: 0;
    }

    .header-section {
        margin-bottom: 40px;
    }

    .header-section h1 {
        font-size: 32px;
    }

    .header-section p {
        font-size: 14px;
    }

    .main-grid {
        gap: 30px;
    }

    .qr-wrapper {
        padding: 24px;
        min-height: 300px;
    }

    .action-buttons {
        grid-template-columns: 1fr;
    }

    .level-buttons {
        gap: 6px;
    }

    .url-input {
        padding: 12px 14px;
        font-size: 13px;
    }

    .btn-generate {
        padding: 14px 16px;
        font-size: 14px;
    }

    .theme-btn {
        width: 36px;
        height: 36px;
        font-size: 14px;
    }

    .modal-content {
        padding: 24px;
    }
}

@media (max-width: 480px) {
    .header-section h1 {
        font-size: 28px;
    }

    .header-section {
        margin-bottom: 30px;
    }

    .color-grid {
        grid-template-columns: 1fr;
    }

    .level-buttons {
        grid-template-columns: repeat(2, 1fr);
    }
}