/* ────────────────────────────────────────────
   D·Tr · Camera Dive (3D page transition)
   カメラが現在画面を貫いて次画面へ潜る遷移
   Pure CSS 3D（perspective + translateZ）、外部依存ゼロ
   ──────────────────────────────────────────── */

*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}
:where(html,body){line-break:strict;word-break:normal;overflow-wrap:break-word}
:where(h1,h2,h3,h4){text-wrap:balance}
:where(p,li){text-wrap:pretty}

:root{
  --bg:#f4f3ee;
  --ink:#0a0a0a;
  --muted:#6a6a6a;
  --line:#d8d6cc;
  --paper:#fff;
  --hi:#ff2d55;
  --alt:#0066ff;
  --font:'DM Sans','Noto Sans JP',sans-serif;
  --mono:'JetBrains Mono',monospace;

  /* ── Component variables ── */
  --cam-perspective:1200px;
  --cam-depth:1500px;                 /* next 画面の待機奥行き */
  --cam-pass:800px;                   /* prev 画面が手前へ飛ぶ距離 */
  --cam-dur:900ms;
  --cam-ease:cubic-bezier(.7,0,.2,1);
  --cam-stage:min(80vh,680px);
}

html{scroll-behavior:smooth}
body{
  background:var(--bg);color:var(--ink);
  font-family:var(--font);font-weight:400;line-height:1.65;
  min-height:100vh;
}
a{color:inherit;text-decoration:none}

/* ─── HEADER ─── */
header.site{
  position:sticky;top:0;z-index:50;background:var(--bg);
  padding:1rem clamp(1.2rem,4vw,3rem);
  display:flex;align-items:center;justify-content:space-between;gap:1rem;
  border-bottom:1px solid var(--ink);
}
.back{font-family:var(--mono);font-size:.78rem;letter-spacing:.18em;display:inline-flex;align-items:center;gap:.6em}
.back .arrow{transition:transform .25s}
.back:hover .arrow{transform:translateX(-.3em)}
.cell-marker{font-family:var(--mono);font-size:.78rem;letter-spacing:.22em;color:var(--hi)}

/* ────────────────────────────────────────────
   COMPONENT: .camera
   ──────────────────────────────────────────── */
.camera{
  position:relative;
  max-width:1200px;margin:clamp(1.5rem,4vw,3rem) auto 0;
  padding:0 clamp(1.2rem,4vw,3rem);
}
.deck{
  position:relative;
  height:var(--cam-stage);
  perspective:var(--cam-perspective);
  perspective-origin:50% 45%;
  border:1px solid var(--ink);
  overflow:hidden;
  background:var(--ink);
}
.screen{
  position:absolute;inset:0;
  display:flex;flex-direction:column;align-items:flex-start;justify-content:center;
  gap:1rem;
  padding:clamp(2rem,6vw,5rem);
  backface-visibility:hidden;
  transform-style:preserve-3d;
  transition:transform var(--cam-dur) var(--cam-ease),
             opacity var(--cam-dur) ease;
  will-change:transform,opacity;
}

/* 3 states */
.screen[data-state="active"]{ transform:translateZ(0);                  opacity:1; z-index:2; }
.screen[data-state="next"]{   transform:translateZ(calc(-1 * var(--cam-depth))); opacity:0; z-index:1; }
.screen[data-state="prev"]{   transform:translateZ(var(--cam-pass));    opacity:0; z-index:1; }

/* per-screen palette */
.screen--a{background:var(--bg);color:var(--ink)}
.screen--b{background:var(--ink);color:#fff}
.screen--c{background:var(--hi);color:#fff}
.screen--d{background:var(--alt);color:#fff}

.screen-no{font-family:var(--mono);font-size:.85rem;letter-spacing:.3em;opacity:.7}
.screen-title{font-weight:700;font-size:clamp(2.6rem,9vw,6.5rem);line-height:.95;letter-spacing:-.02em}
.screen-text{font-size:clamp(.95rem,1.4vw,1.15rem);max-width:34em;opacity:.85;line-height:1.8}

/* ─── controls ─── */
.deck-ui{
  display:flex;align-items:center;justify-content:center;gap:1.4rem;
  margin-top:1.4rem;
}
.deck-btn{
  width:3rem;height:3rem;flex:none;
  border:1px solid var(--ink);background:var(--paper);
  font-family:var(--mono);font-size:1.1rem;color:var(--ink);cursor:pointer;
  transition:transform .2s,box-shadow .2s,background .2s,color .2s;
}
.deck-btn:hover{transform:translate(-2px,-2px);box-shadow:4px 4px 0 var(--hi)}
.deck-btn:disabled{opacity:.3;cursor:default;transform:none;box-shadow:none}
.deck-dots{display:flex;gap:.7rem;align-items:center}
.deck-dot{
  width:.7rem;height:.7rem;border:1px solid var(--ink);background:transparent;
  padding:0;cursor:pointer;transition:background .25s,transform .25s;
}
.deck-dot[aria-current="true"]{background:var(--hi);border-color:var(--hi);transform:scale(1.25)}
.deck-count{
  display:block;text-align:center;margin-top:.9rem;
  font-family:var(--mono);font-size:.74rem;letter-spacing:.25em;color:var(--muted);
}

/* ────────────────────────────────────────────
   END COMPONENT
   ──────────────────────────────────────────── */


/* ─── NOTES ─── */
section{max-width:1100px;margin:0 auto;padding:clamp(3rem,5vw,4.5rem) clamp(1.5rem,4vw,3rem)}
.shou{
  display:flex;align-items:baseline;justify-content:space-between;gap:1rem;flex-wrap:wrap;
  padding-bottom:1rem;border-bottom:1px solid var(--ink);margin-bottom:2.5rem;
}
.shou h2{font-size:clamp(1.3rem,2vw,1.7rem);font-weight:700;letter-spacing:.04em}
.shou .no{font-family:var(--mono);font-size:.78rem;letter-spacing:.25em;color:var(--muted)}
.notes-grid{display:grid;grid-template-columns:1fr;gap:1.2rem;margin-bottom:3rem}
@media(min-width:780px){.notes-grid{grid-template-columns:repeat(3,1fr)}}
.note{position:relative;background:var(--paper);border:1px solid var(--ink);padding:1.5rem 1.4rem 1.4rem}
.note-no{position:absolute;top:1rem;right:1rem;font-family:var(--mono);font-size:.7rem;letter-spacing:.2em;color:var(--muted)}
.note h3{font-size:1.02rem;font-weight:700;margin-bottom:.7rem;letter-spacing:.02em}
.note p{font-size:.86rem;color:var(--muted);line-height:1.8}
.note code{font-family:var(--mono);font-size:.85em;background:var(--bg);padding:.1em .35em;border:1px solid var(--line)}
.sub-h{font-size:1rem;font-weight:700;letter-spacing:.04em;margin:2rem 0 1rem;padding-bottom:.7rem;border-bottom:1px dashed var(--ink)}
.vars{display:grid;grid-template-columns:1fr;gap:0;border:1px solid var(--ink);background:var(--paper)}
.var{display:grid;grid-template-columns:minmax(10rem,auto) 1fr auto;gap:1rem;padding:.8rem 1rem;border-bottom:1px solid var(--line);align-items:center}
.var:last-child{border-bottom:none}
.var code{font-family:var(--mono);font-size:.82rem;color:var(--hi);font-weight:500}
.var span{font-size:.85rem;color:var(--muted);line-height:1.5}
.var span code{color:var(--ink);background:var(--bg);padding:0 .3em;border:1px solid var(--line)}
.var em{font-family:var(--mono);font-size:.78rem;font-style:normal;color:var(--ink);background:var(--bg);padding:.15em .55em;border:1px solid var(--line);white-space:nowrap}
@media(max-width:680px){.var{grid-template-columns:1fr;gap:.3rem;padding:.9rem 1rem}.var em{justify-self:start}}

/* ─── FOOTER ─── */
footer{
  padding:2rem clamp(1.2rem,4vw,3rem) 1.5rem;
  display:flex;flex-wrap:wrap;gap:1rem;justify-content:space-between;align-items:center;
  font-family:var(--mono);font-size:.72rem;letter-spacing:.2em;color:var(--muted);
  border-top:1px solid var(--ink);
}
footer a{color:var(--ink)}

/* Reduced motion: クロスフェードのみ（Z 移動なし） */
@media (prefers-reduced-motion: reduce){
  .screen{transition:opacity .3s ease}
  .screen[data-state="active"]{transform:none}
  .screen[data-state="next"],
  .screen[data-state="prev"]{transform:none;opacity:0}
}