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

:root {
    --bg: #0f172a;
    --surface: #1e293b;
    --surface-hover: #263548;
    --accent: #60a5fa;
    --accent-bold: #3b82f6;
    --accent-glow: rgba(59, 130, 246, 0.15);
    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --text-dim: #64748b;
    --border: rgba(255, 255, 255, 0.08);
    --border-accent: rgba(96, 165, 250, 0.3);
    --error: #f87171;
    --error-bg: rgba(248, 113, 113, 0.1);
    --success: #4ade80;
    --success-bg: rgba(74, 222, 128, 0.1);
    --radius: 10px;
    --radius-sm: 6px;
    --radius-lg: 12px;
    --mono: 'Courier New', Courier, monospace;
    --font: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    --transition: 150ms ease;
}

html {
    font-size: 15px;
}

body {
    font-family: var(--font);
    background: var(--bg);
    color: var(--text-primary);
    min-height: 100vh;
    line-height: 1.5;
    -webkit-font-smoothing: antialiased;
}

/* ===== Header ===== */
.header {
    background: linear-gradient(135deg, #1e3a5f 0%, #2563eb 50%, #7c3aed 100%);
    padding: 24px 0 0;
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: 0 4px 24px rgba(0, 0, 0, 0.3);
}

.header-content {
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 24px;
}

.title-row {
    margin-bottom: 20px;
}

.header h1 {
    font-size: 1.5rem;
    font-weight: 700;
    letter-spacing: -0.01em;
    color: #fff;
}

.subtitle {
    font-size: 0.85rem;
    color: rgba(255, 255, 255, 0.7);
    margin-top: 4px;
    font-weight: 400;
}

.mode-tabs {
    display: flex;
    gap: 2px;
}

.tab {
    display: flex;
    align-items: center;
    gap: 7px;
    padding: 10px 22px;
    background: rgba(255, 255, 255, 0.08);
    border: none;
    border-radius: var(--radius) var(--radius) 0 0;
    color: rgba(255, 255, 255, 0.7);
    font-family: var(--font);
    font-size: 0.85rem;
    font-weight: 500;
    cursor: pointer;
    transition: background var(--transition), color var(--transition);
}

.tab:hover {
    background: rgba(255, 255, 255, 0.14);
    color: #fff;
}

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

/* ===== Container ===== */
.container {
    max-width: 1100px;
    margin: 0 auto;
    padding: 24px;
}

/* ===== Mode Panels ===== */
.mode-panel {
    display: none;
}

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

/* ===== Options Bar ===== */
.options-bar {
    display: flex;
    align-items: center;
    gap: 24px;
    padding: 14px 18px;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    margin-bottom: 20px;
    flex-wrap: wrap;
}

.toggle-option {
    display: flex;
    align-items: center;
    gap: 8px;
    cursor: pointer;
    user-select: none;
}

.toggle-option input {
    display: none;
}

.toggle-switch {
    width: 36px;
    height: 20px;
    background: var(--text-dim);
    border-radius: 10px;
    position: relative;
    transition: background var(--transition);
    flex-shrink: 0;
}

.toggle-switch::after {
    content: '';
    position: absolute;
    width: 16px;
    height: 16px;
    border-radius: 50%;
    background: #fff;
    top: 2px;
    left: 2px;
    transition: transform var(--transition);
}

.toggle-option input:checked + .toggle-switch {
    background: var(--accent-bold);
}

.toggle-option input:checked + .toggle-switch::after {
    transform: translateX(16px);
}

.toggle-label {
    font-size: 0.82rem;
    font-weight: 500;
    color: var(--text-primary);
}

.toggle-hint {
    font-size: 0.72rem;
    color: var(--text-dim);
}

.btn-clear-all {
    margin-left: auto;
}

/* ===== Buttons ===== */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 7px 14px;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    background: var(--surface);
    color: var(--text-secondary);
    font-family: var(--font);
    font-size: 0.78rem;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition);
    white-space: nowrap;
}

.btn:hover {
    background: var(--surface-hover);
    color: var(--text-primary);
    border-color: rgba(255, 255, 255, 0.15);
}

.btn-primary {
    background: var(--accent-bold);
    color: #fff;
    border-color: var(--accent-bold);
}

.btn-primary:hover {
    background: #2563eb;
    border-color: #2563eb;
}

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

.btn-primary:disabled:hover {
    background: var(--accent-bold);
}

.btn-secondary {
    background: transparent;
}

.btn-icon {
    padding: 6px;
    border: 1px solid transparent;
    background: transparent;
    color: var(--text-dim);
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all var(--transition);
    display: inline-flex;
    align-items: center;
    justify-content: center;
}

.btn-icon:hover {
    color: var(--text-primary);
    background: rgba(255, 255, 255, 0.06);
}

.btn-sm {
    padding: 5px 10px;
    font-size: 0.73rem;
}

.btn-swap {
    padding: 8px 20px;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    color: var(--accent);
    font-family: var(--font);
    font-size: 0.82rem;
    font-weight: 600;
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    gap: 6px;
    transition: all var(--transition);
}

.btn-swap:hover {
    background: var(--accent-glow);
    border-color: var(--border-accent);
    color: var(--accent);
}

/* ===== Textarea Panel ===== */
.textarea-panel {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    overflow: hidden;
    margin-bottom: 0;
}

.panel-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 10px 16px;
    border-bottom: 1px solid var(--border);
    background: rgba(255, 255, 255, 0.02);
}

.panel-title {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 0.82rem;
    font-weight: 600;
    color: var(--text-primary);
}

.panel-icon {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 28px;
    height: 22px;
    border-radius: 4px;
    font-size: 0.65rem;
    font-weight: 700;
    letter-spacing: 0.02em;
}

.encode-icon {
    background: rgba(96, 165, 250, 0.15);
    color: var(--accent);
}

.decode-icon {
    background: rgba(124, 58, 237, 0.15);
    color: #a78bfa;
}

.panel-actions {
    display: flex;
    align-items: center;
    gap: 8px;
}

.stats {
    font-size: 0.72rem;
    color: var(--text-dim);
    font-variant-numeric: tabular-nums;
}

textarea {
    width: 100%;
    min-height: 160px;
    padding: 14px 16px;
    background: transparent;
    border: none;
    color: var(--text-primary);
    font-family: var(--font);
    font-size: 0.88rem;
    line-height: 1.6;
    resize: vertical;
    outline: none;
}

textarea.monospace {
    font-family: var(--mono);
    font-size: 0.82rem;
    word-break: break-all;
}

textarea::placeholder {
    color: var(--text-dim);
}

textarea:focus {
    background: rgba(96, 165, 250, 0.03);
}

/* ===== Error Bar ===== */
.error-bar {
    padding: 0;
    max-height: 0;
    overflow: hidden;
    font-size: 0.78rem;
    color: var(--error);
    background: var(--error-bg);
    border-top: 1px solid transparent;
    transition: all 200ms ease;
}

.error-bar.visible {
    padding: 8px 16px;
    max-height: 60px;
    border-top-color: rgba(248, 113, 113, 0.2);
}

/* ===== Swap Row ===== */
.swap-row {
    display: flex;
    align-items: center;
    gap: 16px;
    padding: 12px 0;
}

.encoding-info {
    font-size: 0.76rem;
    color: var(--text-dim);
    display: flex;
    gap: 16px;
    flex-wrap: wrap;
}

.encoding-info span {
    display: inline-flex;
    align-items: center;
    gap: 4px;
}

.encoding-info .overhead {
    color: var(--accent);
    font-weight: 500;
}

/* ===== Copy Feedback ===== */
.copy-toast {
    position: fixed;
    bottom: 24px;
    left: 50%;
    transform: translateX(-50%) translateY(20px);
    padding: 10px 20px;
    background: var(--success-bg);
    border: 1px solid rgba(74, 222, 128, 0.3);
    color: var(--success);
    font-size: 0.82rem;
    font-weight: 500;
    border-radius: var(--radius);
    opacity: 0;
    pointer-events: none;
    transition: all 250ms ease;
    z-index: 1000;
}

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

/* ===== File Mode ===== */
.file-columns {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 24px;
}

.column-title {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 0.95rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 16px;
}

/* ===== Drop Zone ===== */
.drop-zone {
    border: 2px dashed rgba(255, 255, 255, 0.12);
    border-radius: var(--radius-lg);
    padding: 40px 24px;
    text-align: center;
    cursor: pointer;
    transition: all var(--transition);
    background: rgba(255, 255, 255, 0.02);
}

.drop-zone:hover,
.drop-zone.drag-over {
    border-color: var(--accent);
    background: var(--accent-glow);
}

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

.drop-zone:hover .drop-icon,
.drop-zone.drag-over .drop-icon {
    color: var(--accent);
}

.drop-text {
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--text-secondary);
    margin-bottom: 4px;
}

.drop-subtext {
    font-size: 0.78rem;
    color: var(--text-dim);
}

/* ===== File Info Card ===== */
.file-info-card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 14px 16px;
    margin-top: 16px;
}

.file-info-header {
    display: flex;
    align-items: flex-start;
    justify-content: space-between;
}

.file-info-details {
    display: flex;
    flex-direction: column;
    gap: 2px;
}

.file-name {
    font-size: 0.88rem;
    font-weight: 600;
    color: var(--text-primary);
    word-break: break-all;
}

.file-meta {
    font-size: 0.76rem;
    color: var(--text-dim);
}

.file-size-info {
    margin-top: 10px;
    padding-top: 10px;
    border-top: 1px solid var(--border);
    font-size: 0.76rem;
    color: var(--text-secondary);
    display: flex;
    gap: 16px;
    flex-wrap: wrap;
}

.file-size-info span {
    display: inline-flex;
    align-items: center;
    gap: 4px;
}

.file-size-info .overhead {
    color: var(--accent);
    font-weight: 500;
}

.btn-remove-file {
    color: var(--text-dim);
}

.btn-remove-file:hover {
    color: var(--error);
    background: var(--error-bg);
}

/* ===== Image Preview ===== */
.image-preview {
    margin-top: 16px;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    overflow: hidden;
    background: repeating-conic-gradient(
        rgba(255, 255, 255, 0.03) 0% 25%,
        rgba(255, 255, 255, 0.06) 0% 50%
    ) 50% / 16px 16px;
    display: flex;
    align-items: center;
    justify-content: center;
    max-height: 220px;
    padding: 12px;
}

.image-preview img {
    max-width: 100%;
    max-height: 196px;
    object-fit: contain;
    border-radius: 4px;
}

/* ===== Decode Options ===== */
.decode-options {
    margin-top: 16px;
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.field-label {
    font-size: 0.76rem;
    font-weight: 500;
    color: var(--text-secondary);
    margin-bottom: 4px;
    display: block;
}

.text-input {
    width: 100%;
    padding: 8px 12px;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    color: var(--text-primary);
    font-family: var(--mono);
    font-size: 0.82rem;
    outline: none;
    transition: border-color var(--transition);
}

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

.text-input::placeholder {
    color: var(--text-dim);
    font-family: var(--font);
}

.mime-input-group {
    position: relative;
}

.detected-label {
    position: absolute;
    right: 10px;
    top: 50%;
    transform: translateY(-50%);
    font-size: 0.68rem;
    color: var(--success);
    background: var(--success-bg);
    padding: 2px 8px;
    border-radius: 3px;
    font-weight: 500;
}

.btn-download {
    align-self: flex-start;
    padding: 10px 24px;
    font-size: 0.85rem;
}

/* File mode textarea panel spacing */
#file-mode .textarea-panel {
    margin-top: 16px;
}

#file-b64-panel textarea {
    min-height: 120px;
}

#decode-b64-input {
    min-height: 140px;
}

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

/* ===== Toast ===== */
#copy-toast {
    position: fixed;
    bottom: 24px;
    left: 50%;
    transform: translateX(-50%) translateY(20px);
    padding: 10px 20px;
    background: #065f46;
    border: 1px solid rgba(74, 222, 128, 0.3);
    color: var(--success);
    font-family: var(--font);
    font-size: 0.82rem;
    font-weight: 500;
    border-radius: var(--radius);
    opacity: 0;
    pointer-events: none;
    transition: all 250ms ease;
    z-index: 1000;
}

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

/* ===== Responsive ===== */
@media (max-width: 800px) {
    html {
        font-size: 14px;
    }

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

    .options-bar {
        gap: 14px;
    }

    .toggle-hint {
        display: none;
    }

    .header-content {
        padding: 0 16px;
    }

    .container {
        padding: 16px;
    }

    .encoding-info {
        font-size: 0.7rem;
    }
}

@media (max-width: 500px) {
    .panel-actions .stats {
        display: none;
    }

    .options-bar {
        flex-direction: column;
        align-items: flex-start;
    }

    .btn-clear-all {
        margin-left: 0;
    }
}

/* ===== Scrollbar ===== */
::-webkit-scrollbar {
    width: 8px;
    height: 8px;
}

::-webkit-scrollbar-track {
    background: transparent;
}

::-webkit-scrollbar-thumb {
    background: rgba(255, 255, 255, 0.1);
    border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
    background: rgba(255, 255, 255, 0.18);
}