:root {
  --navy: #1a365d;
  --teal: #2c7a7b;
  --ink: #1a2744;
  --soft: #5b6780;
  --paper: #f6f3ec;
  --card: #fffdf8;
  --line: #e4ddd2;
  --good: #2f7a4f;
  --bad: #b3372c;
}
* { box-sizing: border-box; }
html, body { margin: 0; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: var(--paper);
  color: var(--ink);
  line-height: 1.55;
}
.bar {
  background: var(--navy);
  color: #f4efe6;
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  align-items: flex-end;
  padding: 1.1rem 1.2rem;
}
.kicker { margin: 0; font-size: .75rem; letter-spacing: .08em; text-transform: uppercase; opacity: .8; }
.bar h1 { margin: .2rem 0 0; font-size: 1.35rem; }
.meta { margin: 0; color: #c9d4e3; }
.pages {
  display: flex;
  flex-wrap: wrap;
  gap: .35rem;
  padding: .65rem 1rem;
  background: #fff;
  border-bottom: 1px solid var(--line);
  position: sticky;
  top: 0;
  z-index: 2;
}
.dot {
  width: 2rem; height: 2rem;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: #fff;
  font-weight: 700;
  cursor: pointer;
}
.dot.on { background: var(--navy); color: #fff; border-color: var(--navy); }
main { max-width: 820px; margin: 0 auto; padding: 1.1rem 1rem 2.5rem; }
.page {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 1.25rem 1.3rem 1.5rem;
}
h2 { margin: 0 0 .7rem; color: var(--navy); font-size: 1.25rem; }
h3 { margin: 1.1rem 0 .4rem; color: var(--teal); font-size: 1.05rem; }
p { margin: .45rem 0 .7rem; }
.eq { background: #eef5f5; border-left: 4px solid var(--teal); padding: .7rem .9rem; margin: .8rem 0; }
.note { color: var(--soft); font-size: .95rem; }
.page img {
  display: block;
  max-width: 100%;
  height: auto;
  margin: .7rem 0 1rem;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
}
.proof {
  width: 100%;
  border-collapse: collapse;
  margin: .8rem 0 1rem;
  font-size: .95rem;
}
.proof th, .proof td {
  border: 1px solid var(--line);
  padding: .45rem .55rem;
  vertical-align: top;
  text-align: left;
}
.proof th { background: #eef2f6; }
.choice {
  display: block;
  width: 100%;
  text-align: left;
  margin: .35rem 0;
  padding: .65rem .75rem;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  cursor: pointer;
  font-size: .98rem;
}
.choice.good { background: #e7f4ec; border-color: var(--good); }
.choice.bad { background: #fbecea; border-color: var(--bad); }
.feedback { margin-top: .5rem; font-weight: 600; }
.pager {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 1rem;
}
.navbtn {
  border: 1px solid var(--navy);
  background: #fff;
  color: var(--navy);
  font-weight: 700;
  padding: .55rem 1rem;
  border-radius: 999px;
  cursor: pointer;
}
.navbtn.primary { background: var(--teal); border-color: var(--teal); color: #fff; }
.navbtn:disabled { opacity: .4; cursor: default; }
footer { text-align: center; color: var(--soft); font-size: .8rem; padding: 0 1rem 1.5rem; }
.list { padding-left: 1.2rem; }
.list li { margin: .3rem 0; }
.flow {
  display: flex;
  flex-direction: column;
  gap: .35rem;
  max-width: 28rem;
}
.box {
  border: 2px solid var(--navy);
  border-radius: 8px;
  padding: .55rem .7rem;
  background: #fff;
}
.box small { display: block; color: var(--teal); font-weight: 700; }
.arrow { text-align: center; color: var(--navy); font-weight: 800; }