:root {
    --color-bg: #f8fafc;
    --color-surface: #ffffff;
    --color-surface-hover: #f1f5f9;
    --color-border: #e2e8f0;
    --color-text-primary: #1e293b;
    --color-text-secondary: #64748b;
    --color-text-muted: #94a3b8;
    --color-primary: #2563eb;
    --color-primary-hover: #1d4ed8;
    --color-primary-light: #dbeafe;
    --color-error: #dc2626;
    --color-error-bg: #fef2f2;
    --color-success: #059669;
    --color-success-bg: #f0fdf4;
    --color-warning: #d97706;
    --color-shadow: rgba(0, 0, 0, 0.08);
    --color-shadow-lg: rgba(0, 0, 0, 0.12);
    
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-full: 9999px;
    
    --transition-fast: 150ms ease;
    --transition-base: 250ms ease;
    --shadow-sm: 0 1px 2px var(--color-shadow);
    --shadow-md: 0 4px 6px -1px var(--color-shadow), 0 2px 4px -2px var(--color-shadow);
    --shadow-lg: 0 10px 15px -3px var(--color-shadow-lg), 0 4px 6px -4px var(--color-shadow-lg);
}

/* Reset & Base */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background-color: var(--color-bg);
    color: var(--color-text-primary);
    line-height: 1.6;
    min-height: 100vh;
}

/* Layout */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 24px 16px;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Header */
.header {
    text-align: center;
    margin-bottom: 32px;
    padding: 16px 0;
}

.header__title {
    font-size: 2.5rem;
    font-weight: 800;
    color: var(--color-text-primary);
    margin-bottom: 8px;
    letter-spacing: -0.025em;
}

.header__subtitle {
    font-size: 1.125rem;
    color: var(--color-text-secondary);
}

/* Main Layout */
.main {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 24px;
    flex: 1;
    align-items: start;
}

/* Cards */
.card {
    background: var(--color-surface);
    border-radius: var(--radius-lg);
    padding: 24px;
    box-shadow: var(--shadow-md);
    border: 1px solid var(--color-border);
    transition: box-shadow var(--transition-base);
}

.card:hover {
    box-shadow: var(--shadow-lg);
}

.card + .card {
    margin-top: 20px;
}

.card__title {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--color-text-primary);
    margin-bottom: 20px;
    display: flex;
    align-items: center;
    gap: 8px;
}

/* Input Section */
.input-group {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.input-field {
    width: 100%;
    min-height: 120px;
    padding: 16px;
    border: 2px solid var(--color-border);
    border-radius: var(--radius-md);
    font-size: 1rem;
    font-family: inherit;
    resize: vertical;
    transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
    background: var(--color-surface);
    color: var(--color-text-primary);
}

.input-field:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px var(--color-primary-light);
}

.input-field::placeholder {
    color: var(--color-text-muted);
}

.input-field.error {
    border-color: var(--color-error);
    box-shadow: 0 0 0 3px var(--color-error-bg);
}

.input-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 0.875rem;
}

.char-count {
    color: var(--color-text-muted);
}

.char-count.warning {
    color: var(--color-warning);
}

.error-message {
    color: var(--color-error);
    font-weight: 500;
}

/* Customization */
.custom-group {
    margin-bottom: 20px;
}

.custom-group:last-child {
    margin-bottom: 0;
}

.custom-label {
    display: block;
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--color-text-secondary);
    margin-bottom: 10px;
}

/* Color Presets */
.color-presets {
    display: flex;
    gap: 12px;
    flex-wrap: wrap;
}

.preset-btn {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 6px;
    padding: 12px 16px;
    border: 2px solid var(--color-border);
    border-radius: var(--radius-md);
    background: var(--color-surface);
    cursor: pointer;
    transition: all var(--transition-fast);
    font-family: inherit;
    font-size: 0.8125rem;
    color: var(--color-text-secondary);
    min-width: 80px;
}

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

.preset-btn.active {
    border-color: var(--color-primary);
    background: var(--color-primary-light);
    color: var(--color-primary);
    font-weight: 600;
}

.preset-preview {
    width: 32px;
    height: 32px;
    border-radius: 50%;
    border: 2px solid var(--color-border);
}

.preset-btn.active .preset-preview {
    border-color: var(--color-primary);
}

/* Color Pickers */
.custom-colors {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 16px;
}

.color-input-group {
    display: flex;
    align-items: center;
    gap: 10px;
}

.color-picker {
    width: 44px;
    height: 44px;
    border: 2px solid var(--color-border);
    border-radius: var(--radius-sm);
    cursor: pointer;
    background: none;
    padding: 2px;
    transition: border-color var(--transition-fast);
}

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

.color-picker::-webkit-color-swatch-wrapper {
    padding: 0;
}

.color-picker::-webkit-color-swatch {
    border: none;
    border-radius: 4px;
}

.color-text {
    flex: 1;
    padding: 10px 12px;
    border: 2px solid var(--color-border);
    border-radius: var(--radius-sm);
    font-size: 0.875rem;
    font-family: 'Courier New', monospace;
    color: var(--color-text-primary);
    text-transform: uppercase;
    transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.color-text:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px var(--color-primary-light);
}

/* Slider */
.slider {
    width: 100%;
    height: 6px;
    border-radius: var(--radius-full);
    background: var(--color-border);
    outline: none;
    -webkit-appearance: none;
    appearance: none;
    cursor: pointer;
}

.slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 22px;
    height: 22px;
    border-radius: 50%;
    background: var(--color-primary);
    cursor: pointer;
    border: 3px solid var(--color-surface);
    box-shadow: var(--shadow-sm);
    transition: transform var(--transition-fast), box-shadow var(--transition-fast);
}

.slider::-webkit-slider-thumb:hover {
    transform: scale(1.15);
    box-shadow: var(--shadow-md);
}

.slider::-moz-range-thumb {
    width: 22px;
    height: 22px;
    border-radius: 50%;
    background: var(--color-primary);
    cursor: pointer;
    border: 3px solid var(--color-surface);
    box-shadow: var(--shadow-sm);
}

/* Select */
.select-field {
    width: 100%;
    padding: 12px 16px;
    border: 2px solid var(--color-border);
    border-radius: var(--radius-md);
    font-size: 0.9375rem;
    font-family: inherit;
    color: var(--color-text-primary);
    background: var(--color-surface);
    cursor: pointer;
    transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
    appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='24' height='24' viewBox='0 0 24 24' fill='none' stroke='%2364748b' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpolyline points='6 9 12 15 18 9'%3E%3C/polyline%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 12px center;
    background-size: 18px;
    padding-right: 40px;
}

.select-field:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px var(--color-primary-light);
}

.help-text {
    display: block;
    margin-top: 6px;
    font-size: 0.8125rem;
    color: var(--color-text-muted);
}

/* Logo Upload */
.logo-upload-area {
    position: relative;
    border: 2px dashed var(--color-border);
    border-radius: var(--radius-md);
    padding: 24px;
    text-align: center;
    transition: all var(--transition-fast);
    cursor: pointer;
    background: var(--color-bg);
}

.logo-upload-area:hover {
    border-color: var(--color-primary);
    background: var(--color-primary-light);
}

.logo-upload-area.drag-over {
    border-color: var(--color-primary);
    background: var(--color-primary-light);
    border-style: solid;
}

.logo-upload-area.has-logo {
    border-style: solid;
    border-color: var(--color-success);
    background: var(--color-success-bg);
}

.logo-input {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    opacity: 0;
    cursor: pointer;
    z-index: 2;
}

.logo-placeholder {
    pointer-events: none;
}

.upload-icon {
    width: 40px;
    height: 40px;
    color: var(--color-text-muted);
    margin-bottom: 12px;
}

.upload-text {
    font-size: 0.9375rem;
    font-weight: 500;
    color: var(--color-text-secondary);
    margin-bottom: 4px;
}

.upload-hint {
    font-size: 0.875rem;
    color: var(--color-text-muted);
    margin-bottom: 4px;
}

.upload-format {
    font-size: 0.75rem;
    color: var(--color-text-muted);
}

.logo-preview {
    display: none;
    position: relative;
    pointer-events: none;
}

.logo-preview.active {
    display: block;
}

.logo-preview img {
    max-width: 100%;
    max-height: 120px;
    object-fit: contain;
    border-radius: var(--radius-sm);
}

.logo-remove {
    position: absolute;
    top: -8px;
    right: -8px;
    width: 28px;
    height: 28px;
    border-radius: 50%;
    background: var(--color-error);
    border: 2px solid var(--color-surface);
    color: white;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    pointer-events: all;
    z-index: 3;
    transition: transform var(--transition-fast);
}

.logo-remove:hover {
    transform: scale(1.1);
}

.logo-remove svg {
    width: 14px;
    height: 14px;
}

.logo-error {
    margin-top: 8px;
    font-size: 0.875rem;
    color: var(--color-error);
}

/* Preview Panel */
.preview-panel {
    position: sticky;
    top: 24px;
}

.preview-card {
    display: flex;
    flex-direction: column;
    align-items: center;
}

.qr-container {
    width: 100%;
    aspect-ratio: 1;
    max-width: 400px;
    margin: 0 auto;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--color-bg);
    border-radius: var(--radius-md);
    border: 2px solid var(--color-border);
    position: relative;
    overflow: hidden;
}

.qr-placeholder {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 16px;
    color: var(--color-text-muted);
    text-align: center;
    padding: 24px;
}

.qr-placeholder.hidden {
    display: none;
}

.qr-icon {
    width: 64px;
    height: 64px;
    color: var(--color-text-muted);
    opacity: 0.5;
}

.qr-placeholder p {
    font-size: 1rem;
    color: var(--color-text-secondary);
}

.qr-canvas {
    display: none;
    max-width: 100%;
    max-height: 100%;
    border-radius: var(--radius-sm);
}

.qr-canvas.active {
    display: block;
}

.qr-loading {
    display: none;
    flex-direction: column;
    align-items: center;
    gap: 12px;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
}

.qr-loading.active {
    display: flex;
}

.spinner {
    width: 40px;
    height: 40px;
    border: 3px solid var(--color-border);
    border-top-color: var(--color-primary);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* Actions */
.actions-card .card__title {
    margin-bottom: 16px;
}

.actions-group {
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.download-group {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 12px;
}

.share-group {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 12px;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 12px 20px;
    border: none;
    border-radius: var(--radius-md);
    font-size: 0.9375rem;
    font-weight: 500;
    font-family: inherit;
    cursor: pointer;
    transition: all var(--transition-fast);
    text-decoration: none;
    width: 100%;
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

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

.btn-primary:hover:not(:disabled) {
    background: var(--color-primary-hover);
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

.btn-primary:active:not(:disabled) {
    transform: translateY(0);
}

.btn-secondary {
    background: var(--color-surface);
    color: var(--color-text-primary);
    border: 2px solid var(--color-border);
}

.btn-secondary:hover:not(:disabled) {
    background: var(--color-surface-hover);
    border-color: var(--color-primary);
    color: var(--color-primary);
}

.btn-share {
    background: var(--color-surface);
    color: var(--color-text-secondary);
    border: 1px solid var(--color-border);
    padding: 10px 14px;
    font-size: 0.875rem;
}

.btn-share:hover:not(:disabled) {
    background: var(--color-surface-hover);
    border-color: var(--color-primary);
    color: var(--color-primary);
}

.btn-icon {
    width: 18px;
    height: 18px;
    flex-shrink: 0;
}

/* Footer */
.footer {
    text-align: center;
    padding: 32px 0 16px;
    color: var(--color-text-muted);
    font-size: 0.875rem;
    border-top: 1px solid var(--color-border);
    margin-top: 32px;
}

/* Toast */
.toast {
    position: fixed;
    bottom: 32px;
    left: 50%;
    transform: translateX(-50%) translateY(100px);
    background: var(--color-text-primary);
    color: white;
    padding: 14px 24px;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-lg);
    opacity: 0;
    transition: all 0.3s ease;
    z-index: 1000;
    pointer-events: none;
}

.toast.active {
    transform: translateX(-50%) translateY(0);
    opacity: 1;
}

.toast-content {
    display: flex;
    align-items: center;
    gap: 10px;
}

.toast-icon {
    width: 20px;
    height: 20px;
    color: var(--color-success);
}

.toast-message {
    font-size: 0.9375rem;
    font-weight: 500;
}

/* Responsive Design */
@media (max-width: 900px) {
    .main {
        grid-template-columns: 1fr;
    }
    
    .preview-panel {
        position: static;
    }
    
    .qr-container {
        max-width: 300px;
    }
}

@media (max-width: 600px) {
    .container {
        padding: 16px 12px;
    }
    
    .header__title {
        font-size: 1.75rem;
    }
    
    .header__subtitle {
        font-size: 1rem;
    }
    
    .card {
        padding: 16px;
    }
    
    .color-presets {
        gap: 8px;
    }
    
    .preset-btn {
        padding: 8px 12px;
        min-width: 70px;
    }
    
    .custom-colors {
        grid-template-columns: 1fr;
    }
    
    .download-group {
        grid-template-columns: 1fr;
    }
    
    .share-group {
        grid-template-columns: 1fr;
    }
    
    .qr-container {
        max-width: 100%;
    }
}

/* Print Styles */
@media print {
    .controls-panel,
    .actions-card,
    .footer,
    .header__subtitle {
        display: none;
    }
    
    .main {
        grid-template-columns: 1fr;
    }
    
    .qr-container {
        border: none;
        max-width: 100%;
    }
}