:root {
    --ink: #1b1d1f;
    --muted: #6d706f;
    --accent: #185f8d;
    --paper: #fffef9;
    --canvas: #f4f1e8;
    --line: #d9d4c8;
    --green: #2b7a56;
    --amber: #9a6819;
    --red: #a8423c;
}

*,
*::before,
*::after {
    box-sizing: border-box;
}

html {
    min-height: 100%;
}

body {
    min-height: 100vh;
    margin: 0;
    background:
        linear-gradient(rgba(27, 29, 31, 0.035) 1px, transparent 1px),
        linear-gradient(90deg, rgba(27, 29, 31, 0.035) 1px, transparent 1px),
        var(--canvas);
    background-size: 24px 24px;
    color: var(--ink);
    font-family: Inter, -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
    -webkit-font-smoothing: antialiased;
}

a {
    color: inherit;
}

:focus-visible {
    outline: 3px solid rgba(24, 95, 141, 0.3);
    outline-offset: 4px;
}

.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

.board-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    width: min(100% - 40px, 1040px);
    min-height: 72px;
    margin: 0 auto;
    border-bottom: 1px solid rgba(27, 29, 31, 0.14);
}

.board-home {
    display: inline-flex;
    align-items: center;
    gap: 0.55rem;
    min-height: 44px;
    font-size: 0.88rem;
    font-weight: 600;
    text-decoration: none;
}

.board-home:hover {
    color: var(--accent);
}

.board-status {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--muted);
    font-size: 0.78rem;
    font-weight: 600;
}

.status-dot {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background: var(--amber);
    box-shadow: 0 0 0 4px rgba(154, 104, 25, 0.1);
}

.board-status[data-state="ready"] .status-dot,
.board-status[data-state="saved"] .status-dot {
    background: var(--green);
    box-shadow: 0 0 0 4px rgba(43, 122, 86, 0.1);
}

.board-status[data-state="saving"] .status-dot {
    background: var(--amber);
}

.board-status[data-state="error"] .status-dot {
    background: var(--red);
    box-shadow: 0 0 0 4px rgba(168, 66, 60, 0.1);
}

.board-shell {
    width: min(100% - 40px, 900px);
    margin: 0 auto;
    padding: clamp(3.2rem, 8vw, 6.5rem) 0 4rem;
}

.board-intro {
    max-width: 680px;
    margin-bottom: 2rem;
}

.board-kicker {
    margin: 0 0 0.7rem;
    color: var(--accent);
    font-size: 0.72rem;
    font-weight: 700;
    letter-spacing: 0.14em;
}

.board-intro h1 {
    margin: 0;
    font-family: "Noto Serif SC", "Songti SC", serif;
    font-size: clamp(2.7rem, 8vw, 5rem);
    font-weight: 600;
    letter-spacing: -0.04em;
    line-height: 1;
}

.board-intro > p:last-child {
    margin: 1rem 0 0;
    color: var(--muted);
    font-size: 0.95rem;
}

.paper {
    overflow: hidden;
    border: 1px solid rgba(27, 29, 31, 0.14);
    border-radius: 4px;
    background: var(--paper);
    box-shadow: 0 20px 60px rgba(52, 45, 31, 0.09);
}

#board-editor {
    display: block;
    width: 100%;
    min-height: min(58vh, 620px);
    resize: vertical;
    padding: clamp(1.4rem, 4vw, 2.5rem);
    border: 0;
    background:
        repeating-linear-gradient(
            to bottom,
            transparent 0,
            transparent 31px,
            rgba(27, 29, 31, 0.075) 32px
        );
    color: var(--ink);
    font: 400 clamp(1rem, 2vw, 1.08rem) / 2 Inter, "PingFang SC", "Microsoft YaHei", sans-serif;
    outline: 0;
}

#board-editor:disabled {
    cursor: wait;
    opacity: 0.62;
}

#board-editor::placeholder {
    color: #9c9a91;
}

.paper-footer {
    display: flex;
    justify-content: space-between;
    gap: 1rem;
    padding: 0.75rem clamp(1.4rem, 4vw, 2.5rem);
    border-top: 1px solid var(--line);
    color: var(--muted);
    font-size: 0.72rem;
}

.board-notice {
    display: grid;
    grid-template-columns: auto 1fr;
    gap: 0.65rem 1rem;
    margin-top: 1.4rem;
    color: var(--muted);
    font-size: 0.75rem;
    line-height: 1.7;
}

.board-notice strong {
    color: var(--ink);
}

noscript {
    display: block;
    margin: 1rem auto;
    color: var(--red);
    text-align: center;
}

@media (max-width: 640px) {
    .board-header,
    .board-shell {
        width: min(100% - 28px, 900px);
    }

    .board-header {
        min-height: 64px;
    }

    .board-status {
        font-size: 0.72rem;
    }

    .board-intro {
        margin-bottom: 1.4rem;
    }

    #board-editor {
        min-height: 56vh;
    }

    .board-notice {
        grid-template-columns: 1fr;
        gap: 0.2rem;
    }
}