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

:root {
    --primary-color: #4f46e5;
    --primary-hover: #4338ca;
    --secondary-color: #6b7280;
    --bg-color: #f3f4f6;
    --card-bg: #ffffff;
    --text-primary: #1f2937;
    --text-secondary: #6b7280;
    --border-color: #e5e7eb;
    --success-color: #10b981;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
}

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

.app-container {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Header */
.header {
    background: linear-gradient(135deg, var(--primary-color) 0%, #7c3aed 100%);
    color: white;
    padding: 2rem 1rem;
    text-align: center;
}

.header h1 {
    font-size: 2.5rem;
    margin-bottom: 0.5rem;
}

.header .subtitle {
    opacity: 0.9;
    font-size: 1.1rem;
}

/* Main Content */
.main-content {
    flex: 1;
    max-width: 900px;
    margin: 0 auto;
    padding: 2rem 1rem;
    width: 100%;
}

/* Tab Navigation */
.tab-nav {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1.5rem;
    background: var(--card-bg);
    padding: 0.5rem;
    border-radius: 12px;
    box-shadow: var(--shadow);
}

.tab-btn {
    flex: 1;
    padding: 0.875rem 1.5rem;
    border: none;
    background: transparent;
    border-radius: 8px;
    cursor: pointer;
    font-size: 1rem;
    font-weight: 500;
    color: var(--text-secondary);
    transition: all 0.2s ease;
}

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

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

/* Tab Content */
.tab-content {
    display: none;
    background: var(--card-bg);
    border-radius: 12px;
    padding: 2rem;
    box-shadow: var(--shadow);
    margin-bottom: 1.5rem;
}

.tab-content.active {
    display: block;
}

/* Upload Zone */
.upload-zone {
    border: 2px dashed var(--border-color);
    border-radius: 12px;
    padding: 3rem 2rem;
    text-align: center;
    cursor: pointer;
    transition: all 0.2s ease;
}

.upload-zone:hover,
.upload-zone.dragover {
    border-color: var(--primary-color);
    background: rgba(79, 70, 229, 0.05);
}

.upload-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.upload-zone p {
    color: var(--text-secondary);
    margin-bottom: 0.25rem;
}

.upload-hint {
    font-size: 0.875rem;
}

/* Text Options */
.text-options {
    display: flex;
    flex-direction: column;
    gap: 1.25rem;
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.form-group label {
    font-weight: 500;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.form-group input[type="text"],
.form-group select {
    padding: 0.75rem 1rem;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    font-size: 1rem;
    transition: border-color 0.2s ease;
}

.form-group input[type="text"]:focus,
.form-group select:focus {
    outline: none;
    border-color: var(--primary-color);
}

.form-group input[type="color"] {
    width: 100%;
    height: 44px;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    cursor: pointer;
    padding: 4px;
}

.form-group input[type="range"] {
    width: 100%;
    height: 8px;
    border-radius: 4px;
    -webkit-appearance: none;
    appearance: none;
    background: var(--border-color);
}

.form-group input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background: var(--primary-color);
    cursor: pointer;
}

.form-row {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
}

/* Preview Section */
.preview-section {
    background: var(--card-bg);
    border-radius: 12px;
    padding: 2rem;
    box-shadow: var(--shadow);
    margin-bottom: 1.5rem;
}

.preview-section h2 {
    margin-bottom: 1.5rem;
    font-size: 1.25rem;
}

.preview-container {
    display: flex;
    align-items: center;
    gap: 2rem;
    flex-wrap: wrap;
    justify-content: center;
}

.preview-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.5rem;
}

.preview-item canvas {
    border: 1px solid var(--border-color);
    border-radius: 8px;
    background: repeating-conic-gradient(#e5e7eb 0% 25%, transparent 0% 50%) 50% / 16px 16px;
}

.preview-item span {
    font-size: 0.75rem;
    color: var(--text-secondary);
}

.preview-sizes {
    display: flex;
    gap: 1.5rem;
    align-items: flex-end;
}

/* Options Section */
.options-section {
    background: var(--card-bg);
    border-radius: 12px;
    padding: 2rem;
    box-shadow: var(--shadow);
    margin-bottom: 1.5rem;
}

.options-section h2 {
    margin-bottom: 1.5rem;
    font-size: 1.25rem;
}

.options-section h3 {
    font-size: 1rem;
    margin-bottom: 1rem;
    color: var(--text-secondary);
}

.size-options {
    margin-bottom: 2rem;
}

.checkbox-group {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
    gap: 0.75rem;
}

.checkbox-group label {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    cursor: pointer;
    font-size: 0.875rem;
}

.checkbox-group input[type="checkbox"] {
    width: 18px;
    height: 18px;
    accent-color: var(--primary-color);
}

.manifest-options {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    gap: 1rem;
    margin-bottom: 2rem;
    padding-top: 1.5rem;
    border-top: 1px solid var(--border-color);
}

/* Buttons */
.btn {
    padding: 0.875rem 1.5rem;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s ease;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
}

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

.btn-primary:hover {
    background: var(--primary-hover);
    transform: translateY(-1px);
}

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

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

.action-buttons {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
}

/* Code Section */
.code-section {
    background: var(--card-bg);
    border-radius: 12px;
    padding: 2rem;
    box-shadow: var(--shadow);
    margin-bottom: 1.5rem;
}

.code-section h2 {
    margin-bottom: 1rem;
    font-size: 1.25rem;
}

.code-block {
    position: relative;
    background: #1f2937;
    border-radius: 8px;
    padding: 1.5rem;
    overflow-x: auto;
}

.code-block pre {
    color: #e5e7eb;
    font-family: 'Monaco', 'Menlo', 'Ubuntu Mono', monospace;
    font-size: 0.875rem;
    line-height: 1.6;
    margin: 0;
    white-space: pre-wrap;
    word-break: break-all;
}

.btn-copy {
    position: absolute;
    top: 0.75rem;
    right: 0.75rem;
    padding: 0.5rem 0.75rem;
    font-size: 0.75rem;
    background: rgba(255, 255, 255, 0.1);
    color: white;
    border: none;
}

.btn-copy:hover {
    background: rgba(255, 255, 255, 0.2);
}

/* Footer */
.footer {
    background: var(--card-bg);
    padding: 1.5rem;
    text-align: center;
    border-top: 1px solid var(--border-color);
}

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

.footer a {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 500;
}

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

/* Responsive Design */
@media (max-width: 768px) {
    .header h1 {
        font-size: 1.75rem;
    }

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

    .tab-nav {
        flex-direction: column;
    }

    .form-row {
        grid-template-columns: 1fr;
    }

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

    .preview-sizes {
        flex-wrap: wrap;
        justify-content: center;
    }

    .action-buttons {
        flex-direction: column;
    }

    .action-buttons .btn {
        width: 100%;
    }

    .checkbox-group {
        grid-template-columns: 1fr;
    }

    .manifest-options {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 480px) {
    .main-content {
        padding: 1rem 0.75rem;
    }

    .tab-content,
    .preview-section,
    .options-section,
    .code-section {
        padding: 1.5rem 1rem;
    }

    .upload-zone {
        padding: 2rem 1rem;
    }
}

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

.preview-section,
.options-section,
.code-section {
    animation: fadeIn 0.3s ease;
}

/* Toast Notification */
.toast {
    position: fixed;
    bottom: 2rem;
    left: 50%;
    transform: translateX(-50%);
    background: var(--text-primary);
    color: white;
    padding: 0.875rem 1.5rem;
    border-radius: 8px;
    box-shadow: var(--shadow-lg);
    z-index: 1000;
    animation: slideUp 0.3s ease;
}

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateX(-50%) translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateX(-50%) translateY(0);
    }
}