/* ===== CSS Variables & Theming ===== */
:root {
    --primary: #2563eb;
    --primary-hover: #1d4ed8;
    --primary-light: #dbeafe;
    --bg: #f8fafc;
    --bg-card: #ffffff;
    --bg-input: #ffffff;
    --text: #1e293b;
    --text-secondary: #64748b;
    --border: #e2e8f0;
    --shadow: 0 1px 3px rgba(0, 0, 0, 0.08), 0 1px 2px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 4px 12px rgba(0, 0, 0, 0.1);
    --radius: 8px;
    --radius-lg: 12px;
    --transition: 0.2s ease;
    --success: #16a34a;
    --error: #dc2626;
    --warning: #f59e0b;
}

[data-theme="dark"] {
    --bg: #0f172a;
    --bg-card: #1e293b;
    --bg-input: #334155;
    --text: #f1f5f9;
    --text-secondary: #94a3b8;
    --border: #334155;
    --primary-light: #1e3a5f;
    --shadow: 0 1px 3px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 4px 12px rgba(0, 0, 0, 0.4);
}

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

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

/* ===== Header ===== */
.header {
    background: var(--bg-card);
    border-bottom: 1px solid var(--border);
    box-shadow: var(--shadow);
    position: sticky;
    top: 0;
    z-index: 100;
    transition: background var(--transition), border-color var(--transition);
}

.header-inner {
    max-width: 800px;
    margin: 0 auto;
    padding: 16px 20px;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary);
    letter-spacing: -0.02em;
}

.theme-toggle {
    background: var(--bg-input);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 8px 12px;
    cursor: pointer;
    font-size: 1.1rem;
    color: var(--text);
    transition: all var(--transition);
    display: flex;
    align-items: center;
    justify-content: center;
}

.theme-toggle:hover {
    border-color: var(--primary);
    box-shadow: 0 0 0 2px var(--primary-light);
}

.theme-icon-dark {
    display: none;
}

[data-theme="dark"] .theme-icon-light {
    display: none;
}

[data-theme="dark"] .theme-icon-dark {
    display: inline;
}

/* ===== Container ===== */
.container {
    max-width: 800px;
    margin: 0 auto;
    padding: 24px 20px 40px;
}

/* ===== Tabs ===== */
.tabs {
    display: flex;
    gap: 4px;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    padding: 4px;
    margin-bottom: 24px;
    box-shadow: var(--shadow);
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    transition: background var(--transition), border-color var(--transition);
}

.tab {
    flex: 1;
    padding: 10px 16px;
    background: transparent;
    border: none;
    border-radius: var(--radius);
    cursor: pointer;
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--text-secondary);
    transition: all var(--transition);
    white-space: nowrap;
}

.tab:hover {
    color: var(--text);
    background: var(--primary-light);
}

.tab.active {
    background: var(--primary);
    color: #ffffff;
    box-shadow: 0 1px 3px rgba(37, 99, 235, 0.3);
}

/* ===== Tab Panels ===== */
.tab-panel {
    display: none;
    animation: fadeIn 0.25s ease;
}

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

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(4px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.panel-title {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 20px;
    color: var(--text);
}

/* ===== Forms ===== */
.form {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 16px;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    padding: 24px;
    box-shadow: var(--shadow);
    transition: background var(--transition), border-color var(--transition);
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.form-group.full-width {
    grid-column: 1 / -1;
}

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

.form-group input[type="text"],
.form-group input[type="tel"],
.form-group input[type="email"],
.form-group input[type="url"],
.form-group textarea,
.form-group select {
    padding: 10px 12px;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    background: var(--bg-input);
    color: var(--text);
    font-size: 0.9rem;
    transition: all var(--transition);
    outline: none;
    font-family: inherit;
}

.form-group input:focus,
.form-group textarea:focus,
.form-group select:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 3px var(--primary-light);
}

.form-group textarea {
    resize: vertical;
    min-height: 80px;
}

.form-group input[type="color"] {
    width: 100%;
    height: 40px;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 4px;
    cursor: pointer;
    background: var(--bg-input);
}

.form-group input[type="range"] {
    width: 100%;
    accent-color: var(--primary);
}

.form-group input[type="file"] {
    padding: 8px;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    background: var(--bg-input);
    color: var(--text);
    font-size: 0.85rem;
    cursor: pointer;
}

.range-value {
    font-size: 0.8rem;
    color: var(--primary);
    font-weight: 600;
    text-align: center;
}

.checkbox-label {
    display: flex;
    align-items: center;
    gap: 8px;
    cursor: pointer;
    padding-top: 20px;
    font-size: 0.9rem;
    color: var(--text);
}

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

/* ===== Buttons ===== */
.form-actions {
    display: flex;
    gap: 12px;
    padding-top: 8px;
}

.btn {
    padding: 12px 24px;
    border: none;
    border-radius: var(--radius);
    font-size: 0.9rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition);
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    font-family: inherit;
}

.btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
}

.btn-primary {
    background: var(--primary);
    color: #ffffff;
    width: 100%;
}

.btn-primary:hover:not(:disabled) {
    background: var(--primary-hover);
    box-shadow: 0 2px 8px rgba(37, 99, 235, 0.35);
}

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

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

.btn-icon {
    background: var(--bg-input);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 8px;
    cursor: pointer;
    color: var(--text-secondary);
    transition: all var(--transition);
    display: flex;
    align-items: center;
    justify-content: center;
}

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

/* ===== Loading Spinner ===== */
.btn .spinner {
    width: 18px;
    height: 18px;
    border: 2px solid transparent;
    border-top-color: currentColor;
    border-radius: 50%;
    animation: spin 0.6s linear infinite;
}

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

/* ===== Result Area ===== */
.result-area {
    margin-top: 24px;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    padding: 24px;
    text-align: center;
    box-shadow: var(--shadow);
    transition: background var(--transition), border-color var(--transition);
}

.result-area.hidden {
    display: none;
}

.preview-container {
    background: #ffffff;
    border-radius: var(--radius);
    padding: 16px;
    display: inline-block;
    margin-bottom: 16px;
    box-shadow: inset 0 0 0 1px var(--border);
}

.preview-container img {
    max-width: 100%;
    height: auto;
    display: block;
}

/* ===== Decode Specific ===== */
.drop-zone {
    border: 2px dashed var(--border);
    border-radius: var(--radius-lg);
    padding: 48px 24px;
    text-align: center;
    cursor: pointer;
    transition: all var(--transition);
    position: relative;
    background: var(--bg);
}

.drop-zone:hover,
.drop-zone.dragover {
    border-color: var(--primary);
    background: var(--primary-light);
}

.drop-zone-content {
    pointer-events: none;
}

.drop-icon {
    color: var(--text-secondary);
    margin-bottom: 12px;
}

.drop-text {
    font-size: 1rem;
    font-weight: 500;
    color: var(--text);
    margin-bottom: 4px;
}

.drop-subtext {
    font-size: 0.85rem;
    color: var(--text-secondary);
}

.drop-input {
    position: absolute;
    inset: 0;
    opacity: 0;
    cursor: pointer;
}

.decode-preview {
    margin-top: 16px;
    text-align: center;
}

.decode-preview.hidden {
    display: none;
}

.decode-preview img {
    max-width: 200px;
    max-height: 200px;
    border-radius: var(--radius);
    border: 1px solid var(--border);
}

.result-title {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 12px;
    color: var(--text);
}

.decode-output {
    display: flex;
    align-items: flex-start;
    gap: 8px;
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 12px 16px;
}

.decode-data {
    flex: 1;
    font-family: 'SF Mono', Monaco, 'Cascadia Code', monospace;
    font-size: 0.9rem;
    word-break: break-all;
    white-space: pre-wrap;
    text-align: left;
    color: var(--text);
    margin: 0;
}

.decode-type {
    margin-top: 8px;
    font-size: 0.8rem;
    color: var(--text-secondary);
}

/* ===== Toast ===== */
.toast {
    position: fixed;
    bottom: 24px;
    left: 50%;
    transform: translateX(-50%) translateY(20px);
    background: var(--bg-card);
    color: var(--text);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 12px 24px;
    box-shadow: var(--shadow-lg);
    font-size: 0.9rem;
    z-index: 1000;
    opacity: 0;
    transition: all 0.3s ease;
    pointer-events: none;
}

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

.toast.hidden {
    display: block;
    opacity: 0;
}

.toast.success {
    border-left: 3px solid var(--success);
}

.toast.error {
    border-left: 3px solid var(--error);
}

/* ===== SEO Content ===== */
.seo-content {
    max-width: 800px;
    margin: 48px auto 0;
    padding: 0 20px;
}

.seo-inner {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    padding: 32px;
    box-shadow: var(--shadow);
    transition: background var(--transition), border-color var(--transition);
}

.seo-content h2 {
    font-size: 1.3rem;
    font-weight: 700;
    color: var(--text);
    margin-bottom: 12px;
}

.seo-content h3 {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--text);
    margin: 20px 0 10px;
}

.seo-content p {
    font-size: 0.9rem;
    color: var(--text-secondary);
    line-height: 1.7;
    margin-bottom: 8px;
}

.seo-content ul {
    list-style: none;
    padding: 0;
}

.seo-content ul li {
    font-size: 0.9rem;
    color: var(--text-secondary);
    line-height: 1.7;
    padding: 4px 0 4px 20px;
    position: relative;
}

.seo-content ul li::before {
    content: "\2713";
    position: absolute;
    left: 0;
    color: var(--success);
    font-weight: 700;
}

.seo-content details {
    border: 1px solid var(--border);
    border-radius: var(--radius);
    margin-bottom: 8px;
    transition: border-color var(--transition);
}

.seo-content details summary {
    padding: 12px 16px;
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--text);
    cursor: pointer;
    list-style: none;
}

.seo-content details summary::before {
    content: "+";
    display: inline-block;
    width: 20px;
    font-weight: 700;
    color: var(--primary);
}

.seo-content details[open] summary::before {
    content: "\2212";
}

.seo-content details p {
    padding: 0 16px 12px;
    margin: 0;
}

/* ===== Footer ===== */
.footer {
    text-align: center;
    padding: 24px 20px;
    color: var(--text-secondary);
    font-size: 0.85rem;
    border-top: 1px solid var(--border);
    margin-top: 40px;
}

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

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

/* ===== Responsive ===== */
@media (max-width: 640px) {
    .header-inner {
        padding: 12px 16px;
    }

    .logo {
        font-size: 1.25rem;
    }

    .container {
        padding: 16px 12px 32px;
    }

    .tabs {
        border-radius: var(--radius);
        padding: 3px;
        gap: 2px;
    }

    .tab {
        padding: 8px 10px;
        font-size: 0.8rem;
    }

    .form {
        grid-template-columns: 1fr;
        padding: 16px;
        gap: 12px;
    }

    .form-group.full-width {
        grid-column: 1;
    }

    .panel-title {
        font-size: 1.1rem;
    }

    .result-area {
        padding: 16px;
    }

    .drop-zone {
        padding: 32px 16px;
    }
}

@media (max-width: 400px) {
    .tabs {
        flex-wrap: wrap;
    }

    .tab {
        flex: 0 0 auto;
    }
}