:root {
    --font: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    --font-cjk: "PingFang SC", "PingFang TC", "Hiragino Sans GB", "Heiti SC", "Noto Sans CJK SC", serif;
    --bg:     #f5f5f7;
    --fg:     #1a1a1a;
    --border: #ddd;
    --btn-bg: #ffffff;
    --btn-shadow: 0 2px 10px rgba(0,0,0,0.08);
    --accent: #7852ee;
}

* { box-sizing: border-box; margin: 0; padding: 0; }

body {
    font-family: var(--font);
    background: var(--bg);
    color: var(--fg);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    align-items: center;
}

/* ── Header ─────────────────────────────────────────── */
header {
    width: 100%;
    max-width: 480px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1.5rem 1.25rem 0.5rem;
}

h1 {
    font-family: var(--font-cjk);
    font-size: 1.6rem;
    font-weight: 700;
    color: var(--fg);
    letter-spacing: 0.05em;
}

.sync-btn {
    position: relative;
    display: flex;
    align-items: center;
    gap: 0.3rem;
    text-decoration: none;
    font-size: 1.5rem;
    color: var(--accent);
    padding: 0.3rem 0.5rem;
    border-radius: 8px;
    -webkit-tap-highlight-color: transparent;
    transition: background 150ms;
}
.sync-btn:hover { background: rgba(120,82,238,0.08); }
.sync-btn:active { background: rgba(120,82,238,0.16); }

#pending-count {
    font-family: var(--font);
    font-size: 0.72rem;
    font-weight: 700;
    background: var(--accent);
    color: white;
    border-radius: 99px;
    padding: 0.1em 0.45em;
    min-width: 1.3em;
    text-align: center;
    display: inline-block;
}
#pending-count:empty { display: none; }

/* ── Deck buttons ────────────────────────────────────── */
main {
    width: 100%;
    max-width: 480px;
    display: flex;
    flex-direction: column;
    gap: 1rem;
    padding: 1.5rem 1.25rem 2rem;
}

.deck-btn {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 0.3rem;
    background: var(--btn-bg);
    border: 1px solid var(--border);
    border-radius: 16px;
    box-shadow: var(--btn-shadow);
    padding: 1.5rem 1rem;
    text-decoration: none;
    color: var(--fg);
    -webkit-tap-highlight-color: transparent;
    transition: transform 120ms, box-shadow 120ms;
}
.deck-btn:active {
    transform: scale(0.97);
    box-shadow: 0 1px 4px rgba(0,0,0,0.06);
}

.deck-label {
    font-size: 1.2rem;
}