/* 첫 융착 v3: 청사진. 파랑 도면 한 장, 흰 선, 형광 노랑 심선 */

:root {
  --blue: #12409E;
  --white: #FFFFFF;
  --sub: #BFD0F5;
  --accent: #FFE600;
  --error: #FF8A8A;
  --navy: #0B1F4D;

  /* 구간마다 바뀌는 값: 도면 위에서는 흰색, 문의 종이 위에서는 남색 */
  --bg: var(--blue);
  --fg: var(--white);
  --fg-2: var(--sub);

  /* 심선 12색 (TIA-598 순서). 교육 내용이라 가닥 표시에만 씁니다 */
  --c1: #1E6FD9;  /* 청 */
  --c2: #F08A24;  /* 등 */
  --c3: #2FA84F;  /* 녹 */
  --c4: #8A5A2B;  /* 갈 */
  --c5: #8E98A8;  /* 회 */
  --c6: #FFFFFF;  /* 백 */
  --c7: #E03A3A;  /* 적 */
  --c8: #1A1D24;  /* 흑 */
  --c9: #F2CF1D;  /* 황 */
  --c10: #8B4FD6; /* 자 */
  --c11: #F28AB8; /* 분홍 */
  --c12: #35C9C3; /* 청록 */

  --display: "Do Hyeon", sans-serif;
  --sans: "IBM Plex Sans KR", sans-serif;
  --mono: "IBM Plex Mono", "IBM Plex Sans KR", monospace;

  /* 12열 격자 */
  --wrap: 1200px;
  --pad: clamp(20px, 5vw, 48px);
  --gutter: 24px;
  --col: calc((min(100cqw, var(--wrap)) - 2 * var(--pad) - 11 * var(--gutter)) / 12);
  --indent: calc(2 * var(--col) + 2 * var(--gutter));
  --edge: max(var(--pad), calc((100% - var(--wrap)) / 2 + var(--pad)));
  --sec-pad: 64px;

  /* 40px 간격 격자선 */
  --grid: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='40' height='40'%3E%3Cpath d='M0 0h40v1H1v39H0z' fill='%23FFFFFF' fill-opacity='.12'/%3E%3C/svg%3E");

  --bench-svg-h: clamp(72px, 11vw, 120px);
  --bench-h: calc(var(--bench-svg-h) + 37px);
}

*, *::before, *::after { box-sizing: border-box; }

html {
  scroll-padding-top: calc(var(--bench-h) + 24px);
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  background: var(--blue) var(--grid);
  color: var(--fg);
  font-family: var(--sans);
  font-size: 1.0625rem;
  font-weight: 400;
  line-height: 1.8;
  word-break: keep-all;
  overflow-wrap: break-word;
}

main, .site-footer { container-type: inline-size; }

h1, h2, h3, p, ol, ul, dl, dd, figure, fieldset { margin: 0; padding: 0; }
ol, ul { list-style: none; }
fieldset { border: 0; min-width: 0; }
a { color: var(--fg); text-underline-offset: 0.25em; text-decoration-thickness: 1px; }
a:hover { text-decoration-thickness: 2px; }
svg { display: block; }
[hidden] { display: none !important; }

:focus-visible {
  outline: 3px solid var(--accent);
  outline-offset: 3px;
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip-path: inset(50%);
  white-space: nowrap;
}

.skip-link {
  position: absolute;
  left: 12px;
  top: -80px;
  z-index: 30;
  padding: 10px 16px;
  background: var(--accent);
  color: var(--blue);
}
.skip-link:focus { top: 12px; }

/* 스크립트가 켜져 있을 때만 보이는 요소 */
.js-only { display: none; }
.js .js-only { display: block; }

/* ---------- 틀 ---------- */

.wrap {
  max-width: var(--wrap);
  margin-inline: auto;
  padding-inline: var(--pad);
}

.sec { padding-bottom: var(--sec-pad); }

/* 구간 경계: 양 끝에 화살표가 달린 치수선 */
.sec::before {
  content: "";
  display: block;
  height: 9px;
  margin: 0 var(--edge) var(--sec-pad);
  border-inline: 1px solid var(--white);
  background:
    url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='9'%3E%3Cpath d='M0 4.5 12 0v9z' fill='%23FFFFFF'/%3E%3C/svg%3E") left center no-repeat,
    url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='9'%3E%3Cpath d='M12 4.5 0 0v9z' fill='%23FFFFFF'/%3E%3C/svg%3E") right center no-repeat,
    url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='4' height='9'%3E%3Cpath d='M0 4h4v1H0z' fill='%23FFFFFF'/%3E%3C/svg%3E") center repeat-x;
}

.sec-head { margin-bottom: clamp(32px, 5vw, 56px); }
.sec-head p { margin-top: 20px; max-width: 34em; color: var(--fg-2); }

h1, h2, h3 { font-family: var(--display); font-weight: 400; }
h1 {
  max-width: 11em;
  font-size: clamp(2.5rem, 7.2vw, 5rem);
  line-height: 1.1;
}
h2 {
  font-size: clamp(2rem, 4.6vw, 3.25rem);
  line-height: 1.1;
}
h3 {
  font-size: 1.5rem;
  line-height: 1.3;
}

.fine { margin-top: 16px; font-size: 0.875rem; color: var(--fg-2); }

/* ---------- 도면 표제란 ---------- */

.titleblock {
  width: fit-content;
  min-width: min(100%, 17rem);
  margin: 64px 0 0 auto;
  border: 1px solid var(--fg);
  background: var(--bg);
  font-family: var(--mono);
  font-size: 0.8125rem;
  line-height: 1.5;
}
.titleblock > div { display: grid; grid-template-columns: 4.5rem minmax(0, 1fr); }
.titleblock > div + div { border-top: 1px solid var(--fg); }
.titleblock dt { padding: 6px 10px; border-right: 1px solid var(--fg); color: var(--fg-2); }
.titleblock dd { padding: 6px 12px; }

/* ---------- 버튼 ---------- */

.btn {
  display: inline-block;
  padding: 14px 28px;
  border: 1px solid var(--accent);
  border-radius: 0;
  background: var(--accent);
  color: var(--blue);
  font: inherit;
  font-weight: 500;
  line-height: 1.4;
  text-decoration: none;
  cursor: pointer;
}
.btn:hover { background: var(--bg); color: var(--accent); }
.btn:disabled { opacity: 0.45; cursor: not-allowed; }
.btn-line { border-color: var(--fg); background: transparent; color: var(--fg); }
.btn-line:hover { background: var(--fg); color: var(--bg); }

.text-link { font-weight: 500; }

/* ---------- 데모 고지, 머리글 ---------- */

.demo-strip {
  padding: 8px 16px;
  border-bottom: 1px solid var(--white);
  font-size: 0.875rem;
  text-align: center;
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-block: 16px;
}
.logo {
  color: var(--fg);
  font-family: var(--display);
  font-size: 1.5rem;
  line-height: 1.1;
  text-decoration: none;
}

/* ---------- 작업대 ---------- */

.bench {
  position: sticky;
  top: 0;
  z-index: 20;
  background: var(--blue) var(--grid);
  border-block: 1px solid var(--white);
}
.bench-svg { width: 100%; height: var(--bench-svg-h); }

.bench-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  height: 36px;
  border-top: 1px solid var(--white);
  background: var(--blue);
  font-family: var(--mono);
  font-size: 0.8125rem;
}
.bench-caption {
  overflow: hidden;
  color: var(--sub);
  white-space: nowrap;
  text-overflow: ellipsis;
}
.bench-link { flex: none; }

/* 심선은 형광 노랑: 피복은 채운 선, 벗긴 유리는 속이 빈 가는 선 */
.bench .glass { fill: var(--blue); stroke: var(--accent); stroke-width: 1; }
.bench .coat { fill: var(--accent); }
.bench .speck { fill: var(--white); opacity: 0; }
.bench .electrode { fill: var(--blue); stroke: var(--white); stroke-width: 1; opacity: 0; }
.bench .arc { fill: none; stroke: var(--white); stroke-width: 2; stroke-linejoin: miter; opacity: 0; }
.bench .inspect { fill: none; stroke: var(--white); stroke-width: 1; stroke-dasharray: 3 3; opacity: 0; }
.bench .sleeve { opacity: 0; transform: translateX(250px); transform-box: fill-box; transform-origin: center; }
.bench .sleeve rect { fill: rgb(255 255 255 / 0.12); stroke: var(--white); stroke-width: 1; }
.bench .sleeve line { stroke: var(--white); stroke-width: 1; }

.bench .f-left, .bench .f-right, .bench .tip, .bench .scrap, .bench .sleeve {
  transition: transform 0.6s cubic-bezier(0.3, 0.7, 0.2, 1), opacity 0.35s;
}
.bench .speck, .bench .electrode, .bench .arc, .bench .inspect { transition: opacity 0.3s; }

/* 상태 클래스는 누적됩니다: 3단계라면 s1 s2 s3이 모두 붙습니다 */
.bench.s1 .tip-l { transform: translateX(50px); opacity: 0; }
.bench.s1 .tip-r { transform: translateX(-50px); opacity: 0; }
.bench.s1 .speck { opacity: 1; }
.bench.s1 .sleeve { opacity: 1; }
.bench.s2 .speck { opacity: 0; }
.bench.s3 .scrap { transform: translateY(34px); opacity: 0; }
.bench.s4 .f-left { transform: translateX(60px); }
.bench.s4 .f-right { transform: translateX(-60px); }
.bench.s4 .electrode { opacity: 1; }
.bench.s4 .arc { opacity: 1; animation: arc 0.5s steps(2) 4; }
.bench.s5 .arc { opacity: 0; animation: none; }
.bench.s5 .inspect { opacity: 1; }
.bench.s6 .inspect, .bench.s6 .electrode { opacity: 0; }
.bench.s6 .sleeve { transform: translateX(0) scaleY(0.82); }

@keyframes arc {
  50% { opacity: 0.35; }
}

/* ---------- 첫 화면 ---------- */

.hero { padding-block: var(--sec-pad); }
.lead { margin-top: 32px; max-width: 34em; }
.hero-note { margin-top: 16px; max-width: 34em; color: var(--fg-2); }
.hero .btn { margin-top: 40px; }

/* ---------- 심선 가닥 (단계 표시, 12색 공용) ---------- */

.strand {
  display: block;
  height: 10px;
  border: 1px solid var(--fg);
  background: var(--c);
}

/* ---------- 융착 6단계 ---------- */

.step {
  display: grid;
  gap: 24px;
  padding-block: 56px;
  border-top: 1px solid var(--white);
}

.mark { display: flex; align-items: center; gap: 12px; }
.mark-num { font-family: var(--mono); font-size: 2.5rem; font-weight: 400; line-height: 1; }
.mark .strand { flex: 1; }
.mark-name { font-family: var(--mono); font-size: 0.875rem; }

.step h3 { font-size: 2rem; line-height: 1.1; }
.step h3 small { margin-left: 8px; font-family: var(--sans); font-size: 0.9375rem; color: var(--fg-2); }
.step-body > p { margin-top: 16px; max-width: 34em; }

.step-meta { margin-top: 24px; max-width: 34em; }
.step-meta > div { padding-block: 12px; border-top: 1px solid var(--white); }
.step-meta dt { font-family: var(--mono); font-size: 0.8125rem; color: var(--fg-2); }
.step-meta .mistake dd { font-weight: 500; }

.step .titleblock { margin-top: 16px; }

.fig { width: 100%; max-width: 300px; height: auto; }
.fig text { fill: var(--white); font-family: var(--mono); font-size: 11px; }
.fig-glass { fill: var(--blue); stroke: var(--accent); stroke-width: 1; }
.fig-coat { fill: var(--accent); }
.fig-core { fill: var(--white); }
.fig-line { fill: var(--blue); stroke: var(--white); stroke-width: 1; }
.fig-dim { fill: none; stroke: var(--sub); stroke-width: 1; }
.fig-arc { fill: none; stroke: var(--white); stroke-width: 1.5; stroke-linejoin: miter; }
.fig-sleeve { fill: rgb(255 255 255 / 0.12); stroke: var(--white); stroke-width: 1; }
.fig-rod { stroke: var(--white); stroke-width: 1; }

/* ---------- 12색 ---------- */

.order {
  display: grid;
  grid-template-columns: repeat(6, minmax(0, 1fr));
  gap: 24px 8px;
  max-width: 600px;
  counter-reset: order;
}
.order li {
  counter-increment: order;
  padding: 4px;
  font-size: 0.9375rem;
  line-height: 1.4;
}
.order li::before {
  content: counter(order);
  display: block;
  margin-bottom: 6px;
  font-family: var(--mono);
  font-size: 0.8125rem;
  color: var(--fg-2);
}
.order-name { display: block; margin-top: 6px; font-weight: 500; }

.order.is-quiz li:not(.is-filled) .strand { background: transparent; border-style: dashed; }
.order.is-quiz li:not(.is-filled) .order-name { visibility: hidden; }
.order.is-quiz li.is-next { outline: 1px solid var(--white); outline-offset: 0; }
.order li.is-missed .order-name { color: var(--error); }
.order li.is-missed .order-name::after { content: " ✕"; }

.quiz { margin-top: 32px; }
.quiz-pool { display: flex; flex-wrap: wrap; gap: 8px; max-width: 600px; margin-bottom: 24px; }
.quiz-pool button {
  display: flex;
  align-items: center;
  gap: 8px;
  min-height: 44px;
  padding: 8px 14px;
  border: 1px solid var(--white);
  border-radius: 0;
  background: var(--blue);
  color: var(--white);
  font: inherit;
  font-size: 0.9375rem;
  cursor: pointer;
}
.quiz-pool button:hover { outline: 1px solid var(--white); outline-offset: 2px; }
.quiz-pool button:focus-visible { outline: 3px solid var(--accent); outline-offset: 3px; }
.quiz-pool .strand { width: 30px; }
.quiz-status { min-height: 1.8em; max-width: 34em; font-weight: 500; }
.quiz-actions { display: flex; flex-wrap: wrap; align-items: center; gap: 24px; margin-top: 16px; }

/* ---------- 수업 흐름 ---------- */

.flow { max-width: 34em; counter-reset: flow; }
.flow li {
  display: grid;
  grid-template-columns: 2.5rem minmax(0, 1fr);
  padding-block: 20px;
  border-top: 1px solid var(--white);
  counter-increment: flow;
}
.flow li:last-child { border-bottom: 1px solid var(--white); }
.flow li::before {
  content: counter(flow);
  grid-row: span 2;
  font-family: var(--mono);
  font-size: 1.5rem;
  line-height: 1.3;
}
.flow h3, .flow p { grid-column: 2; }
.flow p { margin-top: 4px; color: var(--fg-2); }

.lists {
  display: grid;
  gap: 32px;
  margin-top: 64px;
}
.plain-list { margin-top: 12px; }
.plain-list li { position: relative; padding-left: 20px; }
.plain-list li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.9em;
  width: 10px;
  height: 1px;
  background: var(--white);
}

/* 도면의 주의 사항 칸: 겹선 테두리 */
.warning {
  max-width: 34em;
  margin-top: 64px;
  border: 1px solid var(--white);
  outline: 1px solid var(--white);
  outline-offset: 3px;
  background: var(--blue);
}
.warning-head {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 12px 20px;
  border-bottom: 1px solid var(--white);
  letter-spacing: 0.2em;
}
.warning-head svg { width: 32px; height: 28px; }
.warning-head path { fill: none; stroke: var(--white); stroke-width: 1.5; stroke-linejoin: miter; }
.warning-head .bang { stroke-width: 2; }
.warning ul { padding: 16px 20px 20px; }
.warning li { position: relative; padding-left: 20px; }
.warning li + li { margin-top: 4px; }
.warning li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.72em;
  width: 7px;
  height: 7px;
  background: var(--white);
}

/* ---------- 묻고 답하기 ---------- */

.qa { max-width: 34em; }
.qa > div { padding-block: 24px; border-top: 1px solid var(--white); }
.qa > div:last-child { border-bottom: 1px solid var(--white); }
.qa dt { font-family: var(--display); font-size: 1.375rem; line-height: 1.3; }
.qa dd { margin-top: 8px; color: var(--fg-2); }

/* ---------- 문의 양식: 도면 위에 붙은 흰 종이 ---------- */

.sec-inquiry > .wrap {
  --bg: var(--white);
  --fg: var(--navy);
  --fg-2: var(--navy);
  max-width: none;
  margin-inline: var(--edge);
  padding-block: clamp(40px, 7vw, 80px);
  background: var(--white);
  color: var(--navy);
}
/* 흰 종이 위에서는 노랑 테두리가 보이지 않아, 남색 선과 노랑 바탕으로 포커스를 표시 */
.sec-inquiry :focus-visible { outline-color: var(--navy); }

.form { display: grid; gap: 24px; max-width: 30em; }
.field label, .field legend { display: block; margin-bottom: 8px; font-weight: 500; }
.optional { margin-left: 4px; font-family: var(--mono); font-size: 0.8125rem; font-weight: 400; }

.field input[type="text"],
.field input[type="tel"],
.field textarea {
  display: block;
  width: 100%;
  padding: 12px 14px;
  border: 1px solid var(--navy);
  border-radius: 0;
  background: var(--white);
  color: var(--navy);
  font: inherit;
}
.field input[type="text"]:focus-visible,
.field input[type="tel"]:focus-visible,
.field textarea:focus-visible { background: var(--accent); }
.field textarea { resize: vertical; }
.field ::placeholder { color: var(--navy); font-family: var(--mono); opacity: 0.55; }
.field [aria-invalid="true"] { border-bottom: 4px solid var(--error); }

.radio-row { display: flex; flex-wrap: wrap; gap: 8px 24px; }
.radio-row label, .check { display: flex; align-items: flex-start; gap: 8px; margin: 0; font-weight: 400; }
.radio-row input, .check input {
  flex: none;
  width: 18px;
  height: 18px;
  margin: 0.36em 0 0;
  accent-color: var(--navy);
}

/* 오류 색은 흰 바탕에서 읽히지 않으므로 남색 띠 위에 올림 */
.field-error {
  width: fit-content;
  margin-top: 8px;
  padding: 4px 10px;
  background: var(--navy);
  color: var(--error);
  font-size: 0.9375rem;
}
.form .btn { justify-self: start; border-color: var(--navy); color: var(--navy); }
.form .btn:hover { background: var(--navy); color: var(--accent); }

.done { max-width: 30em; padding: 24px; border: 1px solid var(--navy); }
.done:focus { outline: none; }
.done p { margin-top: 12px; }
.done .btn { margin-top: 24px; }

/* ---------- 바닥글, 모바일 고정 버튼 ---------- */

.site-footer {
  padding-block: 40px 96px;
  border-top: 1px solid var(--white);
  font-size: 0.9375rem;
  color: var(--fg-2);
}
.site-footer p + p { margin-top: 8px; max-width: 34em; }

.mobile-cta {
  position: fixed;
  inset: auto 0 0;
  z-index: 25;
  padding: 20px var(--pad);
  border-top: 1px solid var(--white);
  background: var(--bg);
  color: var(--navy);
  font-weight: 500;
  text-align: center;
  text-decoration: none;
}
/* 흰 판: 위쪽 흰 선과 8px 떨어져 선이 보이게 한다 */
.mobile-cta::before {
  content: "";
  position: absolute;
  inset: 8px var(--pad);
  z-index: -1;
  background: var(--white);
}
.mobile-cta.is-hidden { transform: translateY(100%); }

/* ---------- 넓은 화면 ---------- */

@media (max-width: 859px) {
  .bench-link { display: none; }
}

@media (min-width: 860px) {
  :root { --sec-pad: 112px; }

  .indent { padding-left: calc(var(--pad) + var(--indent)); }
  .wrap > .indent { padding-left: var(--indent); }

  /* 12열: 단계 표시 2, 본문 6, 그림 4 */
  .step {
    grid-template-columns: repeat(12, minmax(0, 1fr));
    gap: 24px var(--gutter);
  }
  .mark { display: block; grid-column: span 2; }
  .mark-num { display: block; font-size: 4rem; }
  .mark .strand { margin-top: 16px; }
  .mark-name { display: block; margin-top: 8px; }
  .step-body { grid-column: span 6; }
  .fig { grid-column: span 4; justify-self: end; margin-top: 8px; }
  .step .titleblock { grid-column: 1 / -1; }

  .lists { grid-template-columns: repeat(2, minmax(0, 17em)); gap: 48px; }

  .site-footer { padding-bottom: 40px; }
  .mobile-cta { display: none; }
}

@media (prefers-reduced-motion: reduce) {
  .bench * { transition: none !important; animation: none !important; }
}