:root{
  --bg: #18372e;
  --bg2: #22453b;
  --bg3: #102720;
  --ink: #111;
  --chalk: rgba(245,247,244,.92);
  --chalkSoft: rgba(245,247,244,.55);
  --line: rgba(255,255,255,.14);
  --shadow: 0 18px 48px rgba(0,0,0,.24);
  --r: 18px;
  --gap: 14px;
  --safeX: max(8px, env(safe-area-inset-left));
  --startPad: 24px; /* 1枚目を少し右から開始 */

  /* 画像は「高さ基準」で表示（横長でも途中で切れない） */
  --imgH: min(86vh, 900px);
  --arrowW: 80px;
}

*{ box-sizing:border-box; }
html,body{ height:100%; }
html{
  background:
    radial-gradient(circle at 20% 18%, rgba(255,255,255,.06), transparent 30%),
    radial-gradient(circle at 82% 24%, rgba(255,255,255,.05), transparent 24%),
    radial-gradient(circle at 50% 72%, rgba(255,255,255,.04), transparent 34%),
    linear-gradient(180deg, var(--bg2), var(--bg) 38%, var(--bg3));
}
body{
  position: relative;
  margin:0;
  overflow-x: hidden;
  background: transparent;
  color: var(--ink);
  font-family: ui-sans-serif, system-ui, -apple-system, "Segoe UI", "Hiragino Kaku Gothic ProN", "Noto Sans JP", "Yu Gothic", sans-serif;
}

body::before,
body::after{
  content:"";
  position: fixed;
  inset: 0;
  pointer-events: none;
}

/* 黒板のムラ・粉感 */
body::before{
  opacity: .5;
  background:
    radial-gradient(circle at 14% 28%, rgba(255,255,255,.08), transparent 18%),
    radial-gradient(circle at 74% 16%, rgba(255,255,255,.06), transparent 16%),
    radial-gradient(circle at 28% 82%, rgba(255,255,255,.05), transparent 20%),
    radial-gradient(circle at 86% 76%, rgba(255,255,255,.06), transparent 22%),
    repeating-linear-gradient(
      0deg,
      rgba(255,255,255,.018) 0px,
      rgba(255,255,255,.018) 1px,
      transparent 1px,
      transparent 4px
    ),
    repeating-linear-gradient(
      90deg,
      rgba(0,0,0,.03) 0px,
      rgba(0,0,0,.03) 2px,
      transparent 2px,
      transparent 6px
    );
  mix-blend-mode: screen;
}

/* 周辺の落ち影 */
body::after{
  background:
    radial-gradient(circle at center, transparent 52%, rgba(0,0,0,.22) 100%);
}

/* フルブリード（画面いっぱい） */
.flow{
  position: relative;
  z-index: 1;
  width: 100vw;
  min-height: 100%;
  margin-left: calc(50% - 50vw);
  margin-right: calc(50% - 50vw);
  padding: 22px 0;
}

.scroller{
  display:flex;
  align-items:center;
  overflow-x:auto;
  gap: var(--gap);
  padding: 10px var(--safeX) 18px;
  padding-left: calc(var(--safeX) + var(--startPad));
  scroll-snap-type: x mandatory;
  scroll-padding-left: calc(var(--safeX) + var(--startPad));
  scroll-behavior: smooth;
  -webkit-overflow-scrolling: touch;
  overscroll-behavior-x: contain;
  scrollbar-width: none;
}
.scroller::-webkit-scrollbar{ display:none; }

/* 1枚 = 1画像（02が2回出ない） */
.slide{
  flex: 0 0 auto;
  scroll-snap-align: center;
}

/* 画像フレーム */
.frame{
  border-radius: var(--r);
  overflow:hidden;
  border: 1px solid rgba(255,255,255,.18);
  box-shadow: var(--shadow);
  background:#fff;

  height: var(--imgH);
  width: auto;
  display:flex;
  align-items:center;
  justify-content:center;
}

/* 重要：切らない（縦を揃えて横は比率で伸びる） */
.frame img{
  display:block;
  height: 100%;
  width: auto;
  object-fit: contain;
}

/* 画像間の矢印 */
.sep{
  flex: 0 0 var(--arrowW);
  display:grid;
  place-items:center;
  font-size: 52px;
  color: var(--chalk);
  text-shadow: 0 0 10px rgba(255,255,255,.08);
  user-select:none;
}

.note{
  flex: 0 0 auto;
  scroll-snap-align: center;
}

.note-card{
  width: clamp(320px, 30vw, 460px);
  min-height: 220px;
  max-height: var(--imgH);
  padding: 28px 30px;
  border: 1px solid rgba(255,255,255,.18);
  border-radius: calc(var(--r) + 2px);
  background:
    linear-gradient(180deg, rgba(39,73,62,.96), rgba(23,52,44,.98));
  box-shadow: var(--shadow);
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 14px;
  position: relative;
}

.note-card::before{
  content:"";
  position:absolute;
  inset: 0;
  border-radius: inherit;
  background:
    radial-gradient(circle at 18% 22%, rgba(255,255,255,.07), transparent 24%),
    radial-gradient(circle at 82% 76%, rgba(255,255,255,.05), transparent 28%),
    repeating-linear-gradient(
      0deg,
      rgba(255,255,255,.02) 0px,
      rgba(255,255,255,.02) 1px,
      transparent 1px,
      transparent 5px
    );
  pointer-events: none;
}

.note-card p{
  position: relative;
  margin: 0;
  color: var(--chalk);
  font-size: clamp(20px, 1.55vw, 28px);
  line-height: 1.85;
  font-weight: 700;
  letter-spacing: .02em;
  text-shadow: 0 0 1px rgba(255,255,255,.22);
}

@media (max-width: 900px){
  .slide,
  .note{
    width: min(calc(100vw - (var(--safeX) * 2) - var(--startPad) - 12px), 560px);
  }

  .frame{
    width: 100%;
    height: auto;
    max-height: min(74dvh, 820px);
  }

  .frame img{
    width: 100%;
    height: auto;
    max-width: 100%;
    max-height: min(74dvh, 820px);
    object-fit: contain;
  }

  .sep{
    flex-basis: 48px;
    font-size: 40px;
  }

  .note-card{
    width: 100%;
    min-height: 180px;
    padding: 22px 20px;
  }

  .note-card p{
    font-size: clamp(16px, 4.2vw, 21px);
    line-height: 1.75;
  }
}

.scroller{
  cursor: grab;
  user-select: none;
}

.scroller.dragging{
  cursor: grabbing;
  scroll-behavior: auto;
  scroll-snap-type: none;
}

.scroller.dragging img{
  pointer-events: none;
}


.back-button{
  position: fixed;
  top: max(2px, env(safe-area-inset-top));
  left: max(2px, env(safe-area-inset-left));
  z-index: 9999;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 5px;
  height: 30px;
  padding: 0 12px;
  border: 1px solid rgba(255,255,255,.20);
  border-radius: 15px;
  background: linear-gradient(180deg, rgba(11,40,33,.90), rgba(8,28,23,.93));
  color: var(--chalk);
  font: inherit;
  font-size: 12px;
  font-weight: 800;
  line-height: 1;
  letter-spacing: 0;
  box-shadow: 0 6px 16px rgba(0,0,0,.16);
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
  backdrop-filter: blur(4px);
}

.back-button:hover{
  transform: translateY(-1px);
}

.back-button:active{
  transform: translateY(0);
}

.back-button:focus-visible{
  outline: 2px solid rgba(255,255,255,.42);
  outline-offset: 2px;
}