/* ===== CSS Reset & Base ===== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    /* Colors */
    --primary-color: #1DA1F2;
    --primary-dark: #1a91da;
    --secondary-color: #14171a;
    --background: #f7f9fa;
    --surface: #ffffff;
    --border: #e1e8ed;
    --text-primary: #14171a;
    --text-secondary: #657786;
    --error: #e0245e;
    --success: #17bf63;

    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;

    /* Border Radius */
    --radius-sm: 4px;
    --radius-md: 8px;
    --radius-lg: 12px;
    --radius-full: 9999px;

    /* Shadows */
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px rgba(0, 0, 0, 0.1);

    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-base: 250ms ease;
}

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

/* ===== Container ===== */
.container {
    max-width: 100%;
    margin: 0 auto;
    padding: var(--spacing-sm);
}

/* ===== Header ===== */
.header {
    text-align: center;
    padding: var(--spacing-lg) var(--spacing-sm);
    background: var(--surface);
    border-bottom: 1px solid var(--border);
    margin-bottom: var(--spacing-md);
}

.header-title {
    font-size: 1.75rem;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: var(--spacing-xs);
}

.header-description {
    font-size: 0.95rem;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto;
}

/* ===== Main Content Layout ===== */
.main-content {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-md);
}

/* ===== Section Title ===== */
.section-title {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
    color: var(--text-primary);
}

/* ===== Upload Area ===== */
.upload-area {
    background: var(--surface);
    border: 2px dashed var(--border);
    border-radius: var(--radius-lg);
    padding: var(--spacing-xl);
    text-align: center;
    transition: all var(--transition-base);
    cursor: pointer;
}

.upload-area.dragover {
    border-color: var(--primary-color);
    background: rgba(29, 161, 242, 0.05);
}

.upload-prompt {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--spacing-sm);
}

.upload-icon {
    width: 64px;
    height: 64px;
    color: var(--primary-color);
}

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

.file-input-label {
    display: inline-block;
    padding: var(--spacing-sm) var(--spacing-md);
    background: var(--primary-color);
    color: white;
    border-radius: var(--radius-md);
    font-weight: 500;
    cursor: pointer;
    transition: background var(--transition-fast);
}

.file-input-label:hover {
    background: var(--primary-dark);
}

.upload-hint {
    font-size: 0.875rem;
    color: var(--text-secondary);
}

/* ===== Editor Section ===== */
.editor-section {
    background: var(--surface);
    border-radius: var(--radius-lg);
    padding: var(--spacing-md);
    box-shadow: var(--shadow-sm);
}

.editor-canvas-container {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
}

.main-canvas {
    width: 100%;
    max-width: 400px;
    height: 400px;
    margin: 0 auto;
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    cursor: move;
    touch-action: none;
    background: var(--surface);
}

/* ===== Image Controls ===== */
.image-controls {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.control-group {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-xs);
}

.control-label {
    font-size: 0.95rem;
    font-weight: 500;
    color: var(--text-primary);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.slider {
    width: 100%;
    height: 44px;
    -webkit-appearance: none;
    appearance: none;
    background: transparent;
    cursor: pointer;
}

.slider::-webkit-slider-track {
    width: 100%;
    height: 8px;
    background: var(--border);
    border-radius: var(--radius-full);
}

.slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 24px;
    height: 24px;
    background: var(--primary-color);
    border-radius: var(--radius-full);
    cursor: pointer;
    margin-top: -8px;
}

.slider::-moz-range-track {
    width: 100%;
    height: 8px;
    background: var(--border);
    border-radius: var(--radius-full);
}

.slider::-moz-range-thumb {
    width: 24px;
    height: 24px;
    background: var(--primary-color);
    border-radius: var(--radius-full);
    cursor: pointer;
    border: none;
}

.control-buttons {
    display: flex;
    gap: var(--spacing-sm);
    flex-wrap: wrap;
}

/* ===== Buttons ===== */
.btn {
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: var(--radius-md);
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-fast);
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-xs);
    min-height: 44px;
}

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

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

.btn-secondary {
    background: var(--surface);
    color: var(--text-primary);
    border: 1px solid var(--border);
}

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

.btn-icon {
    width: 20px;
    height: 20px;
}

/* ===== Preview Section ===== */
.preview-section {
    background: var(--surface);
    border-radius: var(--radius-lg);
    padding: var(--spacing-md);
    box-shadow: var(--shadow-sm);
}

.preview-grid {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
}

.preview-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--spacing-xs);
    padding: var(--spacing-md);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    background: var(--background);
}

.preview-label {
    font-weight: 600;
    font-size: 0.95rem;
    color: var(--text-primary);
}

.preview-canvas {
    border-radius: var(--radius-full);
    background: white;
}

.preview-large {
    width: 200px;
    height: 200px;
}

.preview-medium {
    width: 48px;
    height: 48px;
}

.preview-small {
    width: 24px;
    height: 24px;
}

.preview-size-label {
    font-size: 0.875rem;
    color: var(--text-secondary);
}

/* ===== Background Section ===== */
.background-section {
    background: var(--surface);
    border-radius: var(--radius-lg);
    padding: var(--spacing-md);
    box-shadow: var(--shadow-sm);
}

.bg-tabs {
    display: flex;
    gap: var(--spacing-xs);
    margin-bottom: var(--spacing-md);
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
}

.bg-tab {
    padding: var(--spacing-sm) var(--spacing-md);
    background: var(--background);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    font-size: 0.95rem;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-fast);
    white-space: nowrap;
    min-height: 44px;
}

.bg-tab.active {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

.bg-tab:hover:not(.active) {
    background: var(--surface);
}

.bg-panel {
    display: none;
}

.bg-panel.active {
    display: block;
}

.color-picker-group {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-sm);
}

.color-input {
    width: 60px;
    height: 44px;
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    cursor: pointer;
}

.gradient-controls,
.pattern-colors {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.radio-group {
    display: flex;
    gap: var(--spacing-md);
}

.radio-label {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    cursor: pointer;
    min-height: 44px;
}

.pattern-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-md);
}

.pattern-btn {
    padding: var(--spacing-md);
    background: var(--background);
    border: 2px solid var(--border);
    border-radius: var(--radius-md);
    font-size: 0.95rem;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-fast);
    min-height: 44px;
}

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

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

.preset-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--spacing-sm);
}

.preset-item {
    height: 80px;
    border-radius: var(--radius-md);
    cursor: pointer;
    border: 3px solid transparent;
    transition: all var(--transition-fast);
    position: relative;
    overflow: hidden;
}

.preset-item:hover {
    border-color: var(--primary-color);
    transform: scale(1.05);
}

.preset-item.active {
    border-color: var(--primary-color);
    box-shadow: var(--shadow-md);
}

.preset-label {
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    background: rgba(0, 0, 0, 0.7);
    color: white;
    padding: var(--spacing-xs);
    font-size: 0.75rem;
    text-align: center;
}

.opacity-control {
    margin-top: var(--spacing-md);
    padding-top: var(--spacing-md);
    border-top: 1px solid var(--border);
}

/* ===== Download Section ===== */
.download-section {
    background: var(--surface);
    border-radius: var(--radius-lg);
    padding: var(--spacing-md);
    box-shadow: var(--shadow-sm);
}

.download-buttons {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-sm);
}

.download-hint {
    font-size: 0.875rem;
    color: var(--text-secondary);
    text-align: center;
}

/* ===== Loading Overlay ===== */
.loading-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.5);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-sm);
    color: white;
    z-index: 9999;
}

.spinner {
    width: 48px;
    height: 48px;
    border: 4px solid rgba(255, 255, 255, 0.3);
    border-top-color: white;
    border-radius: var(--radius-full);
    animation: spin 1s linear infinite;
}

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

/* ===== Toast Messages ===== */
.toast {
    position: fixed;
    bottom: var(--spacing-lg);
    left: 50%;
    transform: translateX(-50%);
    background: var(--secondary-color);
    color: white;
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-lg);
    opacity: 0;
    transition: opacity var(--transition-base);
    pointer-events: none;
    z-index: 10000;
}

.toast.show {
    opacity: 1;
}

.toast.error {
    background: var(--error);
}

.toast.success {
    background: var(--success);
}

/* ===== Tablet Layout (768px - 1023px) ===== */
@media (min-width: 768px) {
    .container {
        padding: var(--spacing-md);
    }

    .header-title {
        font-size: 2.25rem;
    }

    .header-description {
        font-size: 1rem;
    }

    .preview-grid {
        flex-direction: row;
        justify-content: space-around;
    }

    .preview-item {
        flex: 1;
    }

    .pattern-grid,
    .preset-grid {
        grid-template-columns: repeat(3, 1fr);
    }

    .download-buttons {
        flex-direction: row;
    }

    .download-buttons .btn {
        flex: 1;
    }
}

/* ===== Desktop Layout (1024px+) ===== */
@media (min-width: 1024px) {
    .container {
        max-width: 1400px;
        padding: var(--spacing-lg);
    }

    .main-content {
        flex-direction: row;
        align-items: flex-start;
    }

    .editor-section {
        flex: 1;
        max-width: 50%;
    }

    .preview-section {
        flex: 1;
        max-width: 50%;
    }

    .preview-grid {
        flex-direction: column;
    }

    .pattern-grid {
        grid-template-columns: repeat(3, 1fr);
    }

    .preset-grid {
        grid-template-columns: repeat(5, 1fr);
    }

    .main-canvas {
        max-width: 500px;
        height: 500px;
    }
}

/* ===== Touch Device Optimizations ===== */
@media (hover: none) and (pointer: coarse) {
    .btn,
    .bg-tab,
    .pattern-btn,
    .color-input,
    .radio-label {
        min-height: 44px;
        min-width: 44px;
    }

    .slider {
        height: 44px;
    }
}

/* ===== Upload Section ===== */
.upload-section {
    margin-bottom: var(--spacing-md);
}

.upload-section-title {
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: var(--spacing-sm);
}

/* ===== Background Image Controls ===== */
.bg-image-controls {
    background: var(--surface);
    border: 2px solid var(--border);
    border-radius: var(--radius-md);
    padding: var(--spacing-md);
}

.bg-image-controls .control-group {
    margin-bottom: var(--spacing-sm);
}

.bg-image-controls .control-buttons {
    display: flex;
    gap: var(--spacing-sm);
}

.bg-image-controls .control-buttons .btn {
    flex: 1;
}

/* ===== Section Header ===== */
.section-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--spacing-sm);
}

.btn-small {
    padding: 0.5rem 1rem;
    font-size: 0.875rem;
}

/* ===== X-Style Post Preview ===== */
.x-preview-section {
    background: var(--surface);
    border-radius: var(--radius-lg);
    padding: var(--spacing-md);
    box-shadow: var(--shadow-sm);
    margin-top: var(--spacing-md);
}

.x-post-container {
    position: relative;
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    overflow: hidden;
    background: #15202b;
}

.x-post-background {
    width: 100%;
    height: 200px;
    position: relative;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    overflow: hidden;
}

.x-background-canvas {
    width: 100%;
    height: 100%;
    object-fit: cover;
    cursor: grab;
}

.x-background-canvas:active {
    cursor: grabbing;
}

.x-post {
    background: #15202b;
    color: #ffffff;
    padding: var(--spacing-md);
    position: relative;
}

.x-post-header {
    display: flex;
    align-items: flex-start;
    gap: var(--spacing-sm);
    margin-top: -40px;
    margin-bottom: var(--spacing-md);
}

.x-avatar-container {
    flex-shrink: 0;
    border: 4px solid #15202b;
    border-radius: var(--radius-full);
    background: #15202b;
}

.x-avatar {
    width: 80px;
    height: 80px;
    border-radius: var(--radius-full);
    display: block;
}

.x-user-info {
    display: flex;
    flex-direction: column;
    margin-top: 40px;
}

.x-user-name {
    font-size: 1.125rem;
    font-weight: 700;
    color: #ffffff;
}

.x-user-handle {
    font-size: 0.9375rem;
    color: #8b98a5;
}

.x-post-content {
    font-size: 0.9375rem;
    line-height: 1.5;
    color: #ffffff;
    margin-bottom: var(--spacing-sm);
}

.x-post-content p {
    margin-bottom: var(--spacing-xs);
}

.x-post-footer {
    font-size: 0.9375rem;
    color: #8b98a5;
    padding-top: var(--spacing-sm);
    border-top: 1px solid #38444d;
}

.x-post-time {
    font-size: 0.875rem;
}

/* ===== Footer ===== */
.footer {
    background: var(--surface);
    border-top: 1px solid var(--border);
    padding: var(--spacing-lg) var(--spacing-sm);
    margin-top: var(--spacing-xl);
}

.footer-content {
    max-width: 1400px;
    margin: 0 auto;
    text-align: center;
}

.footer-text {
    font-size: 0.95rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-sm);
}

.footer-links {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-sm);
}

.footer-link {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-xs);
    padding: var(--spacing-xs) var(--spacing-md);
    color: var(--text-primary);
    text-decoration: none;
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    font-size: 0.95rem;
    font-weight: 500;
    transition: all var(--transition-fast);
    background: var(--background);
}

.footer-link:hover {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.footer-icon {
    width: 20px;
    height: 20px;
}

.footer-copyright {
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin-top: var(--spacing-sm);
}

/* ===== Utility Classes ===== */
.hidden {
    display: none !important;
}

.text-center {
    text-align: center;
}

.mt-1 {
    margin-top: var(--spacing-sm);
}

.mb-1 {
    margin-bottom: var(--spacing-sm);
}