:root{--ink:#14110f;--sub:#8a8279;--paper:#fbfaf7;--line:#e6e1d8;--bar:60px;--foot:52px}
*{box-sizing:border-box}
html,body{margin:0;padding:0;height:100%;overscroll-behavior:none}
body.bk{font-family:"Noto Serif JP","Hiragino Mincho ProN",serif;color:var(--ink);background:var(--paper);
  -webkit-text-size-adjust:100%;overflow:hidden}

/* ---- 上の帯 ---- */
.bk-bar{position:fixed;top:0;left:0;right:0;height:var(--bar);z-index:30;display:flex;align-items:center;gap:14px;
  padding:0 18px;background:rgba(251,250,247,.94);backdrop-filter:blur(8px);border-bottom:1px solid var(--line)}
.bk-home{display:inline-flex;align-items:center;gap:7px;text-decoration:none;color:var(--ink);
  border:1px solid var(--line);background:#fff;border-radius:2px;padding:6px 13px 6px 11px;white-space:nowrap}
.bk-home:hover{border-color:var(--ink)}
.bk-home .ar{font-size:15px;line-height:1}
.bk-home .tx{font-size:12px;letter-spacing:.06em}
.bk-toc-btn,.bk-tool{appearance:none;border:1px solid var(--line);background:#fff;color:var(--ink);
  font-family:inherit;font-size:12px;padding:6px 12px;border-radius:2px;cursor:pointer;white-space:nowrap}
.bk-toc-btn:hover,.bk-tool:hover{border-color:var(--ink)}
.bk-book-title{flex:1;text-align:center;font-size:13px;letter-spacing:.24em;color:var(--sub)}
.bk-tools{display:flex;gap:6px}

/* ---- 閉じた本（開いたときの右ページの位置に表紙が置かれている） ---- */
.bk-cover{position:fixed;inset:var(--bar) 0 0;z-index:20;background:var(--paper);perspective:2600px;
  transition:background .45s ease}
.bk-cover.is-gone{pointer-events:none;background:transparent}
.bk-cover-inner{position:absolute;inset:0;opacity:0;transition:opacity .32s ease}
body.bk-ready .bk-cover-inner{opacity:1}   /* 版面が決まってから表紙とボタンを出す */
/* 表紙の1枚。開くと右へめくれて消える */
.bk-book1{position:absolute;transform-origin:right center;transform-style:preserve-3d;cursor:pointer;
  width:var(--pw,400px);height:var(--ph,576px);top:var(--py,60px);left:var(--px,50%);
  transition:transform 1.05s cubic-bezier(.4,.02,.24,1)}
.bk-book1-face{position:absolute;inset:0;backface-visibility:hidden;background:#fff;overflow:hidden;
  display:grid;place-items:center;box-shadow:0 2px 5px rgba(20,17,15,.10),0 18px 44px rgba(20,17,15,.20)}
.bk-book1-back{transform:rotateY(180deg);background:#f7f6f2;border:1px solid var(--line)}
.bk-book1 img{position:absolute;inset:0;width:100%;height:100%;object-fit:fill}   /* 枠を装丁の比にするので余白は出ない */
.bk-book1-txt{display:grid;place-items:center;gap:14px;width:min(58vh,420px);height:min(64vh,620px);background:#f2f1ed}
.bk-book1-txt span{font-size:11px;letter-spacing:.4em;color:var(--sub)}
.bk-book1-txt b{font-size:34px;letter-spacing:.16em}
.bk-cover.is-gone .bk-book1{transform:rotateY(176deg)}   /* その場で右へめくれる（本は動かない） */
.bk-cover.is-gone{transition:background .5s ease .5s}
.bk-cover-side{position:absolute;left:var(--sx,50%);right:0;top:0;bottom:0;
  display:flex;flex-direction:column;align-items:center;justify-content:center;gap:18px;padding:0 24px;text-align:center}
.bk-cover-sub{font-size:12px;color:var(--sub);letter-spacing:.14em;margin:0;transition:opacity .3s ease}
.bk-cover-act{display:flex;gap:10px;justify-content:center;transition:opacity .3s ease}
@media(max-width:820px){
  .bk-cover-side{left:0;right:0;top:auto;bottom:12px;flex-direction:row;gap:12px;justify-content:center}
}
.bk-cover.is-gone .bk-cover-sub,.bk-cover.is-gone .bk-cover-act{opacity:0}
.bk-open,.bk-resume{appearance:none;border:1px solid var(--ink);background:var(--ink);color:#fff;font-family:inherit;
  font-size:14px;letter-spacing:.16em;padding:13px 34px;border-radius:2px;cursor:pointer}
.bk-resume{background:#fff;color:var(--ink)}
@media(max-width:700px){
  .bk-cover-inner{gap:14px}
  .bk-open,.bk-resume{font-size:13px;padding:12px 24px}
}

/* ---- 本文の舞台 ---- */
.bk-stage{position:fixed;inset:var(--bar) 0 0;display:block}
.bk-paper{position:absolute;top:0;left:var(--sidew,0px);right:0;bottom:var(--foot);
  display:flex;align-items:center;justify-content:center;padding:26px clamp(14px,3vw,40px) 20px}
.bk-src{display:none}

/* 1冊＝紙を並べた台 */
.bk-book{position:relative;display:flex;gap:0;height:100%;perspective:2600px;
  box-shadow:0 1px 3px rgba(20,17,15,.05),0 10px 26px rgba(20,17,15,.07)}
body[data-mode="tate"] .bk-book{flex-direction:row-reverse}   /* 和書は右のページが先 */
/* 見開きの綴じ目（紙は接し、谷の陰だけを落とす） */
.bk-book::after{content:"";position:absolute;top:0;bottom:0;left:50%;transform:translateX(-50%);
  width:56px;pointer-events:none;z-index:3;opacity:0;transition:opacity .3s;
  background:linear-gradient(90deg,rgba(20,17,15,0),rgba(20,17,15,.05) 38%,rgba(20,17,15,.09) 50%,rgba(20,17,15,.05) 62%,rgba(20,17,15,0))}
body.is-spread .bk-book::after{opacity:1}
body.is-spread[data-mode="tate"] #sheet-r{border-left:none}
body.is-spread[data-mode="tate"] #sheet-l{border-right:none}
body.is-spread[data-mode="yoko"] #sheet-r{border-right:none}
body.is-spread[data-mode="yoko"] #sheet-l{border-left:none}
/* ノド（綴じ目側）は余白を広く取る＝本と同じ */
body.is-spread[data-mode="tate"] #sheet-r{padding-left:var(--nodo,54px)}
body.is-spread[data-mode="tate"] #sheet-l{padding-right:var(--nodo,54px)}
body.is-spread[data-mode="yoko"] #sheet-r{padding-right:var(--nodo,54px)}
body.is-spread[data-mode="yoko"] #sheet-l{padding-left:var(--nodo,54px)}
body.is-spread .bk-face-nodo-l{padding-left:var(--nodo,54px)}
body.is-spread .bk-face-nodo-r{padding-right:var(--nodo,54px)}

/* 本を開くときの動き
   ページは回転させない。表紙が退くにつれて、下からそのまま現れる。 */
body.bk-measuring .bk-paper,body.bk-measuring .bk-side,body.bk-measuring .bk-foot{transition:none !important}
body.bk-closed .bk-paper{opacity:0}
.bk-paper{opacity:1;transition:opacity .62s ease}
body.bk-closed .bk-side{opacity:0}
.bk-side{opacity:1;transition:opacity .6s ease .3s}
body.bk-closed .bk-foot{opacity:0}
.bk-foot{transition:opacity .6s ease .3s}

/* 1ページ＝1枚の紙 */
.bk-sheet{position:relative;background:#fff;border:1px solid var(--line);border-radius:1px;
  padding:var(--pt,42px) var(--pf,46px) var(--pb,48px);overflow:hidden;flex:0 0 auto}
body:not(.is-spread) .bk-book{box-shadow:0 1px 3px rgba(20,17,15,.05),0 8px 22px rgba(20,17,15,.06)}
.bk-win{position:relative;overflow:hidden;height:100%;width:100%}
.bk-flow{position:absolute;top:0;bottom:0;right:0;
  writing-mode:vertical-rl;font-size:var(--fs,17px);line-height:var(--lhpx,35px);letter-spacing:.05em}
/* 行送りは全体で同じにする（ページの切れ目が必ず行の間に来るように） */
.bk-flow *{line-height:inherit}
body[data-mode="yoko"] .bk-flow{writing-mode:horizontal-tb;left:0;right:auto;
  width:var(--colw,320px);column-width:var(--colw,320px);column-gap:0;column-fill:auto;height:100%}
.bk-spacer{break-before:column;break-after:column;height:100%}
.bk-nombre{position:absolute;left:0;right:0;bottom:11px;text-align:center;font-size:10.5px;color:var(--sub);letter-spacing:.14em}

/* めくり中の紙（表と裏の2面を持つ） */
.bk-sheet-turn{position:absolute;top:0;z-index:8;visibility:hidden;transform-style:preserve-3d}
.bk-sheet-turn.is-run{visibility:visible;transition:transform var(--turn,.78s) cubic-bezier(.42,0,.3,1)}
.bk-face{position:absolute;inset:0;backface-visibility:hidden;background:#fff;border:1px solid var(--line);
  padding:var(--pt,42px) var(--pf,46px) var(--pb,48px);overflow:hidden;box-shadow:0 2px 8px rgba(20,17,15,.10),0 16px 44px rgba(20,17,15,.14)}
.bk-face-back{transform:rotateY(180deg)}
.bk-sheet-shade{position:absolute;inset:0;pointer-events:none;opacity:0;
  background:linear-gradient(90deg,rgba(20,17,15,.24),rgba(20,17,15,.02) 62%)}
.bk-face-back .bk-sheet-shade{background:linear-gradient(270deg,rgba(20,17,15,.24),rgba(20,17,15,.02) 62%)}
.bk-sheet-turn.is-run .bk-sheet-shade{opacity:1;transition:opacity var(--turn,.78s) ease}

/* 1ページ目＝本の表紙 */
/* 縦書きは軸が入れ替わる：主軸＝上下、交差軸＝左右 */
.bk-titlepage{display:flex;height:100%}
body[data-mode="tate"] .bk-titlepage{justify-content:center;align-items:flex-start}
body[data-mode="yoko"] .bk-titlepage{justify-content:center;align-items:center}
.bk-titlepage img{display:block;max-width:100%;max-height:100%;
  box-shadow:0 1px 2px rgba(20,17,15,.06),0 6px 20px rgba(20,17,15,.10)}

/* 章 */
.bk-ch{break-inside:avoid-column}
/* 余白はすべて行送りの倍数（＝行の位置がずれない） */
.bk-ch-head{margin:0;padding:0}
body[data-mode="tate"] .bk-ch-head{margin:0 0 0 var(--lead2,70px)}
body[data-mode="yoko"] .bk-ch-head{margin:0 0 var(--lead2,70px)}
.bk-ch-num{display:block;font-size:.72em;letter-spacing:.3em;color:var(--sub);margin:0}
.bk-ch-title{font-size:1.34em;font-weight:600;letter-spacing:.1em;margin:0}
.bk-ch-body p{margin:0;text-indent:1em}
/* 本文中の小見出し（・で始まる行）——前後に1行アキ、少し大きく */
.bk-ch-body p.bk-lead{font-size:1.16em;font-weight:600;letter-spacing:.09em;text-indent:0;
  margin-block-start:var(--lhpx,35px);margin-block-end:var(--lhpx,35px)}
.bk-ch-body p.bk-lead:first-child{margin-block-start:0}
.bk-ch-body img{max-width:min(58vh,420px);height:auto;display:block;margin:0}
.bk-ch-body h2,.bk-ch-body h3{font-size:1.1em;font-weight:600;margin:0}
.bk-ch-body a{color:inherit}

/* 巻末 */
.bk-end{display:grid;place-items:center}
.bk-end-inner{text-align:center;writing-mode:horizontal-tb}
.bk-end-mark{font-size:34px;letter-spacing:.3em;margin:0 0 28px}
.bk-end-txt{font-size:14px;line-height:2.2;color:var(--sub);margin:0 0 30px}
.bk-end-link{font-size:14px;color:var(--ink)}

/* 綴じ目（見開きのとき） */


/* めくり操作の当たり */
/* めくる当たり：綴じ目を境に、左半分と右半分の全体 */
.bk-nav{position:absolute;top:0;bottom:var(--foot);border:none;background:transparent;cursor:pointer;z-index:3;
  -webkit-tap-highlight-color:transparent}
/* 紙はクリックを通す（本文の目次リンクだけ拾う） */
.bk-sheet,.bk-sheet-turn{pointer-events:none}
.bk-jump{pointer-events:auto}
.bk-nav:disabled{cursor:default}



/* ---- 下の帯 ---- */
.bk-foot{position:absolute;left:0;right:0;bottom:0;height:var(--foot);padding:0 clamp(20px,4vw,64px);
  display:flex;flex-direction:column;justify-content:center;gap:7px;background:var(--paper);border-top:1px solid var(--line)}
.bk-progress{height:2px;background:var(--line);border-radius:2px;overflow:hidden}
.bk-progress-in{height:100%;width:0;background:var(--ink);transition:width .42s ease}
.bk-foot-row{display:flex;justify-content:space-between;font-size:11px;color:var(--sub);letter-spacing:.08em}

/* ---- 画面わきの目次（広い画面のみ） ---- */
.bk-side{display:none}
@media(min-width:1180px){
  body.bk-reading{--sidew:212px}
  body.bk-reading.bk-side-off{--sidew:0px}
  body.bk-side-off .bk-side{display:none}
  .bk-side{display:block;position:absolute;top:0;left:0;bottom:var(--foot);width:212px;z-index:6;background:var(--paper);
    padding:26px 16px 20px 22px;overflow-y:auto;border-right:1px solid var(--line)}
  .bk-side-h{font-size:10.5px;letter-spacing:.3em;color:var(--sub);margin:0 0 14px}
  .bk-side-list{list-style:none;margin:0;padding:0}
  .bk-side-list li{margin:0}
  .bk-side-list button{display:flex;gap:9px;align-items:baseline;width:100%;text-align:left;background:none;border:none;
    font-family:inherit;font-size:12.5px;line-height:1.6;color:var(--sub);padding:7px 2px;cursor:pointer;border-radius:2px}
  .bk-side-list button:hover{color:var(--ink);background:rgba(20,17,15,.035)}
  .bk-side-list .n{font-size:10px;min-width:14px;text-align:right;font-variant-numeric:tabular-nums}
  .bk-side-list li.is-now button{color:var(--ink);font-weight:600}
  .bk-side-list li.is-now .n{color:var(--ink)}
}

/* 本文の目次からのジャンプ（線は引かず、触れたときだけ色を変える） */
.bk-jump{cursor:pointer;transition:opacity .15s}
.bk-jump:hover{opacity:.55}

/* ---- 目次 ---- */
.bk-toc{position:fixed;inset:0;z-index:40;background:rgba(20,17,15,.32);display:grid;place-items:stretch}
.bk-toc[hidden]{display:none}
.bk-toc-inner{background:var(--paper);width:min(460px,86vw);height:100%;padding:26px 24px 24px;overflow:auto;
  box-shadow:0 0 40px rgba(0,0,0,.18);animation:tocin .28s ease}
@keyframes tocin{from{transform:translateX(-24px);opacity:.4}to{transform:none;opacity:1}}
.bk-toc-h{font-size:12px;letter-spacing:.34em;color:var(--sub);margin:0 0 18px}
.bk-toc-list{list-style:none;margin:0 0 24px;padding:0;counter-reset:c}
.bk-toc-list li{border-bottom:1px solid var(--line)}
.bk-toc-list button{width:100%;display:flex;align-items:baseline;gap:14px;background:none;border:none;
  font-family:inherit;font-size:15px;color:var(--ink);text-align:left;padding:13px 2px;cursor:pointer}
.bk-toc-list button:hover{color:var(--sub)}
.bk-toc-list .n{font-size:11px;color:var(--sub);min-width:18px;text-align:right}
.bk-toc-list li.is-now button{font-weight:600}
.bk-toc-close{appearance:none;border:1px solid var(--line);background:#fff;font-family:inherit;font-size:13px;
  padding:11px 20px;border-radius:2px;cursor:pointer;width:100%}

@media(max-width:430px){
  .bk-bar{gap:7px;padding:0 10px}
  .bk-home{padding:5px 9px 5px 8px;gap:5px}
  .bk-home .tx{font-size:11px;letter-spacing:.02em}
  .bk-home .ar{font-size:13px}
  .bk-toc-btn,.bk-tool{padding:5px 8px;font-size:11px}
  .bk-tools{gap:4px}
}
@media(max-width:700px){
  :root{--bar:52px;--foot:46px}
  .bk-face{padding:var(--pt,26px) var(--pf,22px) var(--pb,30px)}
  .bk-bar{gap:10px;padding:0 12px}
  .bk-book-title{display:none}
  .bk-paper{padding:14px 12px 12px}
  .bk-sheet{--pt:26px;--pf:22px;--pb:30px}
}