/* =================================================================
 * 22. Timeline — chronological chronicle (templates/timeline.html)
 *
 * Designed to read like a bound annual: each year is a chapter
 * heading framed by hair + double rules (matching .proof-masthead),
 * each entry hangs from a continuous vertical spine on the left so
 * the eye registers time literally flowing down the page. Day in
 * arabic + month in Chinese stack like a calendar tear-off; titles
 * use the body serif with proper editorial rhythm.
 * ================================================================= */
.proof-timeline {
    display: flex;
    flex-direction: column;
    gap: var(--wp--preset--spacing--64, 4rem);
    margin-top: var(--wp--preset--spacing--32);
}

/* ---- Year header: chapter divider, masthead vocabulary ---- */
.proof-timeline__year {
    display: flex;
    flex-direction: column;
    gap: var(--wp--preset--spacing--32);
}
.proof-timeline__year-head {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}
.proof-timeline__year-row {
    display: grid;
    grid-template-columns: 1fr auto 1fr;
    align-items: center;
    gap: var(--wp--preset--spacing--24, 1.5rem);
    padding: 0.5rem 0 0.75rem;
}
.proof-timeline__year-rule {
    display: block;
    height: 1px;
    background: var(--wp--preset--color--line);
}
.proof-timeline__year-rule--hair {
    height: 1px;
    background: var(--wp--preset--color--text-primary);
    opacity: 0.55;
}
.proof-timeline__year-rule--double {
    height: 4px;
    background: transparent;
    border-top: 1px solid var(--wp--preset--color--text-primary);
    border-bottom: 1px solid var(--wp--preset--color--text-primary);
}
.proof-timeline__year-stack {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.25em;
}
.proof-timeline__year-num {
    font-family: var(--font-serif);
    font-size: clamp(2.4rem, 6vw, 3.6rem);
    font-weight: 700;
    margin: 0;
    letter-spacing: 0.04em;
    line-height: 1;
    text-align: center;
    color: var(--wp--preset--color--text-primary);
}
.proof-timeline__year-arabic {
    font-family: var(--font-mono);
    font-size: var(--wp--preset--font-size--xxs);
    color: var(--wp--preset--color--text-muted);
    letter-spacing: 0.18em;
    line-height: 1;
    font-feature-settings: "tnum" 1;
}
.proof-timeline__year-flank {
    display: flex;
    flex-direction: column;
    gap: 0.15em;
    font-family: var(--font-mono);
    font-size: var(--wp--preset--font-size--xxs);
    color: var(--wp--preset--color--text-muted);
    letter-spacing: 0.12em;
    text-transform: uppercase;
    line-height: 1.2;
}
.proof-timeline__year-flank--left { justify-self: end; text-align: right; }
.proof-timeline__year-flank--right { justify-self: start; text-align: left; }
.proof-timeline__year-flank-line { display: block; }

/* ---- The chronological list: continuous vertical spine ---- */
.proof-timeline__list {
    list-style: none;
    margin: 0;
    padding: 0;
    display: flex;
    flex-direction: column;
}

/* Each item: [date column] [spine] [body] grid. The spine is a
 * pseudo-rule rendered per item but visually continuous because
 * items butt against each other with no gap. */
.proof-timeline__item {
    display: grid;
    grid-template-columns: 4.5em 1px 1fr;
    column-gap: var(--wp--preset--spacing--24, 1.5rem);
    padding: 1.4rem 0;
    border-bottom: 1px solid var(--wp--preset--color--line);
    align-items: start;
}
.proof-timeline__item:last-child { border-bottom: 0; }

/* ---- Date as a calendar tear-off: day large, month small ---- */
.proof-timeline__date {
    display: flex;
    flex-direction: column;
    align-items: flex-end;
    gap: 0.15em;
    text-align: right;
    font-feature-settings: "lnum" 1, "tnum" 1;
}
.proof-timeline__day {
    font-family: var(--font-serif);
    font-size: clamp(1.6rem, 3.2vw, 2.1rem);
    font-weight: 600;
    line-height: 1;
    color: var(--wp--preset--color--text-primary);
    letter-spacing: -0.01em;
}
.proof-timeline__month {
    font-family: var(--font-serif);
    font-size: var(--wp--preset--font-size--xs);
    color: var(--wp--preset--color--text-muted);
    letter-spacing: 0.08em;
    line-height: 1;
}

/* ---- Vertical spine: hairline running through the column ---- */
.proof-timeline__spine {
    display: block;
    align-self: stretch;
    width: 1px;
    background: var(--wp--preset--color--text-primary);
    opacity: 0.35;
    /* Negative top/bottom margins reach into the item's own padding
     * so adjacent spines visually connect, forming one unbroken rule
     * down the column. */
    margin-top: -1.4rem;
    margin-bottom: -1.4rem;
    min-height: calc(100% + 2.8rem);
    position: relative;
}
/* Bullet glyph at the date row — the editorial "tick" anchoring
 * each entry to the spine. Sits at the day-number's baseline so
 * the eye reads day + tick + title as a single cross-line. */
.proof-timeline__spine::before {
    content: "";
    position: absolute;
    left: 50%;
    top: 1.4rem;
    transform: translate(-50%, 50%);
    width: 7px;
    height: 7px;
    background: var(--wp--preset--color--text-primary);
    border-radius: 50%;
}

/* ---- Entry body ---- */
.proof-timeline__body {
    display: flex;
    flex-direction: column;
    gap: 0.4rem;
    min-width: 0;
    padding-top: 0.1rem;
}

/* Kicker above the title: "#064 · § 笔记" — small mono cluster that
 * the eye can sweep down for fast indexing while the serif title
 * carries the editorial weight. The "#" prefix on the issue NO.
 * doubles as a permalink anchor (li id="noNNN"). */
.proof-timeline__kicker {
    display: flex;
    align-items: baseline;
    gap: 0.5em;
    font-family: var(--font-mono);
    font-size: var(--wp--preset--font-size--xxs);
    color: var(--wp--preset--color--text-muted);
    letter-spacing: 0.06em;
    line-height: 1;
}
.proof-timeline__kicker .proof-timeline__no {
    font-feature-settings: "tnum" 1;
    color: var(--wp--preset--color--text-primary);
    text-decoration: none;
    font-weight: 600;
    letter-spacing: 0.04em;
}
.proof-timeline__kicker .proof-timeline__no:hover {
    color: var(--wp--preset--color--accent, var(--wp--preset--color--text-primary));
}
.proof-timeline__sep { color: var(--wp--preset--color--line); }
.proof-timeline__section {
    color: var(--wp--preset--color--text-muted);
    text-decoration: none;
    letter-spacing: 0.04em;
}
.proof-timeline__section:hover { color: var(--wp--preset--color--text-primary); }

.proof-timeline__title {
    font-family: var(--font-serif);
    font-size: var(--wp--preset--font-size--md);
    font-weight: 500;
    color: var(--wp--preset--color--text-primary);
    text-decoration: none;
    line-height: 1.5;
    border-bottom: 1px solid transparent;
    transition: border-color 0.15s ease;
    align-self: flex-start;
}
.proof-timeline__title:hover {
    border-bottom-color: var(--wp--preset--color--text-primary);
}
.proof-timeline__excerpt {
    font-family: var(--font-serif);
    font-size: var(--wp--preset--font-size--sm);
    color: var(--wp--preset--color--text-muted);
    margin: 0;
    font-style: italic;
    line-height: 1.6;
}

@media (max-width: 600px) {
    .proof-timeline {
        gap: var(--wp--preset--spacing--40, 3rem);
    }
    .proof-timeline__year-row {
        grid-template-columns: 1fr;
        gap: 0.5rem;
        text-align: center;
    }
    .proof-timeline__year-flank--left,
    .proof-timeline__year-flank--right {
        justify-self: center;
        text-align: center;
        flex-direction: row;
        gap: 0.4em;
    }
    .proof-timeline__item {
        grid-template-columns: 3.5em 1px 1fr;
        column-gap: 1rem;
        padding: 1.1rem 0;
    }
    .proof-timeline__spine {
        margin-top: -1.1rem;
        margin-bottom: -1.1rem;
        min-height: calc(100% + 2.2rem);
    }
    .proof-timeline__spine::before { top: 1.1rem; }
    .proof-timeline__day { font-size: 1.4rem; }
}