/* ============================================================
   Layout — 合乎周礼

   Single-page centered layout with a two-pane translation
   area that stacks on narrow viewports.
   ============================================================ */

body {
    display: flex;
    flex-direction: column;
    align-items: center;
    background-color: var(--color-bg-primary);
    background-image:
        radial-gradient(ellipse at 50% 0%, rgba(201, 169, 110, 0.06) 0%, transparent 70%),
        radial-gradient(ellipse at 85% 100%, rgba(139, 37, 0, 0.03) 0%, transparent 50%);
}

/* ── App Container ─────────────────────────────────────── */
.app-container {
    width: 100%;
    max-width: var(--max-content-width);
    margin: 0 auto;
    padding: var(--space-4) var(--space-5);
    display: flex;
    flex-direction: column;
    gap: var(--space-5);
    flex: 1;
}

/* ── Header ────────────────────────────────────────────── */
.app-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding-top: var(--space-2);
    padding-bottom: var(--space-2);
    border-bottom: 1px solid var(--color-border-light);
    user-select: none;
}

.header-left {
    display: flex;
    align-items: center;
    gap: var(--space-3);
}

.header-right {
    text-align: right;
    max-width: 320px;
}

.header-tagline {
    font-size: var(--text-xs);
    color: var(--color-text-tertiary);
    font-family: var(--font-serif-cn);
    letter-spacing: 0.03em;
    line-height: var(--leading-relaxed);
}

.header-icon {
    width: 36px;
    height: 36px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    color: var(--color-seal);
    font-family: var(--font-serif-cn);
    font-weight: 700;
    line-height: 1;
}

.header-title-group {
    display: flex;
    flex-direction: column;
}

.header-title {
    font-size: var(--text-xl);
    font-weight: var(--weight-semibold);
    color: var(--color-text-primary);
    letter-spacing: 0.04em;
}

.header-subtitle {
    font-size: var(--text-xs);
    color: var(--color-text-tertiary);
    letter-spacing: 0.06em;
    margin-top: 1px;
}

/* ── Controls Section ──────────────────────────────────── */
.controls-section {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--space-2);
}

/* ── Translation Panes ─────────────────────────────────── */
.translation-panes {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--space-5);
    align-items: start;
    min-height: 280px;
}

@media (max-width: 680px) {
    .translation-panes {
        grid-template-columns: 1fr;
        min-height: auto;
    }
}

/* ── Pane base ─────────────────────────────────────────── */
.pane {
    background: var(--color-bg-secondary);
    border: var(--border-thin);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-sm);
    transition: border-color var(--transition-base),
                box-shadow var(--transition-base);
    position: relative;
    overflow: hidden;
}

.pane:focus-within {
    border-color: var(--color-accent);
    box-shadow: var(--shadow-focus);
}

/* ── Input Pane ────────────────────────────────────────── */
.input-pane {
    padding: var(--space-4);
    min-height: 260px;
    display: flex;
    flex-direction: column;
}

.input-pane textarea {
    flex: 1;
    background: transparent;
    font-family: var(--font-sans);
    font-size: var(--text-base);
    line-height: var(--leading-relaxed);
    color: var(--color-text-primary);
    resize: none;
    min-height: 200px;
    border: none;
    outline: none;
}

.input-pane textarea::placeholder {
    color: var(--color-text-tertiary);
    font-family: var(--font-serif-cn);
    font-style: normal;
    opacity: 0.7;
}

.input-char-count {
    text-align: right;
    font-size: var(--text-xs);
    color: var(--color-text-tertiary);
    margin-top: var(--space-2);
    user-select: none;
}

.input-char-count.over-limit {
    color: var(--color-error);
}

/* ── Output Pane ────────────────────────────────────────── */
.output-pane {
    padding: 0;
    min-height: 260px;
    display: flex;
    flex-direction: column;
}

/* Decorative top border — like a scroll edge */
.output-pane::before {
    content: '';
    display: block;
    height: 3px;
    background: linear-gradient(
        90deg,
        transparent 0%,
        var(--color-accent-light) 15%,
        var(--color-accent) 50%,
        var(--color-accent-light) 85%,
        transparent 100%
    );
    border-radius: var(--radius-lg) var(--radius-lg) 0 0;
    flex-shrink: 0;
}

.output-pane-body {
    position: relative;
    flex: 1;
    padding: var(--space-4);
    overflow-y: auto;
    font-family: var(--font-serif-cn);
    font-size: var(--text-lg);
    line-height: var(--leading-loose);
    color: var(--color-text-primary);
    word-break: break-word;
}

/* ── Output pane states ────────────────────────────────── */
.output-placeholder {
    display: flex;
    align-items: center;
    justify-content: center;
    height: 100%;
    min-height: 200px;
    color: var(--color-text-tertiary);
    font-family: var(--font-serif-cn);
    font-size: var(--text-base);
    user-select: none;
}

.output-loading {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: var(--space-4);
    height: 100%;
    min-height: 200px;
}

.output-error {
    color: var(--color-error);
    font-family: var(--font-sans);
    font-size: var(--text-sm);
}

/* ── Copy Button ───────────────────────────────────────── */
.copy-btn {
    position: absolute;
    top: var(--space-4);
    right: var(--space-4);
    display: flex;
    align-items: center;
    gap: var(--space-1);
    padding: var(--space-1) var(--space-3);
    background: var(--color-bg-primary);
    border: var(--border-thin);
    border-radius: var(--radius-sm);
    font-size: var(--text-xs);
    color: var(--color-text-secondary);
    opacity: 0;
    transition: opacity var(--transition-base),
                background var(--transition-fast),
                border-color var(--transition-fast);
    z-index: 2;
}

.output-pane:hover .copy-btn,
.copy-btn.copied {
    opacity: 1;
}

.copy-btn:hover {
    background: var(--color-bg-hover);
    border-color: var(--color-accent);
}

.copy-btn.copied {
    color: var(--color-success);
    border-color: var(--color-success);
    opacity: 1;
}

/* ── Classical Toggle Button ─────────────────────────────── */
.classical-toggle-btn {
    position: absolute;
    top: var(--space-3);
    left: var(--space-3);
    display: flex;
    align-items: center;
    gap: var(--space-1);
    padding: var(--space-1) var(--space-3);
    background: var(--color-bg-primary);
    border: var(--border-thin);
    border-radius: var(--radius-sm);
    font-size: var(--text-xs);
    color: var(--color-text-secondary);
    font-family: var(--font-serif-cn);
    letter-spacing: 0.06em;
    transition: background var(--transition-fast),
                border-color var(--transition-fast),
                color var(--transition-fast);
    z-index: 2;
    cursor: pointer;
    user-select: none;
}

.classical-toggle-btn:hover {
    background: var(--color-bg-hover);
    border-color: var(--color-accent);
    color: var(--color-accent);
}

.classical-toggle-btn:active {
    transform: scale(0.96);
}

.classical-toggle-btn.wenyanwen-active {
    color: var(--color-seal);
    border-color: var(--color-seal);
}

/* ── Options Row ───────────────────────────────────────── */
.options-row {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--space-2);
}

.option-group {
    display: flex;
    align-items: center;
    gap: var(--space-2);
    flex-wrap: wrap;
    justify-content: center;
}

.option-label {
    font-size: var(--text-sm);
    color: var(--color-text-secondary);
    font-family: var(--font-serif-cn);
    letter-spacing: 0.04em;
    user-select: none;
    margin-right: var(--space-1);
}

/* ── Action Row ────────────────────────────────────────── */
.action-row {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-2);
}