/* 레이아웃: 회로도 격자 바탕. 한 줄 소개 → 흐름 그림 → 기호 만들기 → 회로 돌려 보기 → 다룰 수 있는 회로 → AI와 함께 */
:root {
  --bg: #f4f7f7;
  --sheet: #ffffff;
  --ink: #13211f;
  --muted: #586866;
  --line: #d3dddc;
  --grid: #e3eaea;
  --accent: #0f7c78;
  --accent-soft: #dcefed;
  --ai: #b7700a;
  --ai-soft: #fbefd9;
  --w-pos: #d23b2f;
  --w-zero: #2f62c9;
  --w-ph1: #b8613f;
  --w-ph2: #1d8f8a;
  --w-ph3: #9a8a2c;
  --w-contact: #7a3fc0;
  --w-contact-halo: #e6d9f7;
  --w-coil: #f6d7b4;
  --w-diag: #e07a12;
  --font-body: "IBM Plex Sans KR", "Malgun Gothic", "Apple SD Gothic Neo", system-ui, sans-serif;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0d1514; --sheet: #142020; --ink: #dce8e6; --muted: #92a5a2; --line: #2a3b3a; --grid: #172524;
    --accent: #4dbdb5; --accent-soft: #163634; --ai: #f0b04a; --ai-soft: #3a2c14;
    --w-pos: #ff6b5e; --w-zero: #6a96ff; --w-ph1: #e08a66; --w-ph2: #4dbdb5; --w-ph3: #cdbb55;
    --w-contact: #b48aef; --w-contact-halo: #33274a; --w-coil: #5a4024; --w-diag: #ff9a3c;
    color-scheme: dark;
  }
}
* { box-sizing: border-box; }
body {
  margin: 0;
  background-color: var(--bg);
  background-image:
    linear-gradient(var(--grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid) 1px, transparent 1px);
  background-size: 20px 20px;
  color: var(--ink);
  font-family: var(--font-body);
  font-size: 15px;
  line-height: 1.65;
}
.page {
  max-width: 1040px;
  margin: 0 auto;
  padding-block: 40px 56px;
  padding-left: max(16px, env(safe-area-inset-left, 0px));
  padding-right: max(16px, env(safe-area-inset-right, 0px));
  display: grid;
  gap: 28px;
}
h1, h2, h3 { margin: 0; text-wrap: balance; }
p { margin: 0; }
a { color: var(--accent); }
a:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

.head { display: grid; gap: 14px; }
.eyebrow { font-size: 12.5px; letter-spacing: 0.08em; color: var(--muted); }
h1 { font-size: clamp(34px, 6vw, 52px); font-weight: 700; letter-spacing: -0.02em; line-height: 1.1; }
h1 .dot { color: var(--accent); }
.lede { font-size: 17.5px; max-width: 60ch; }
.chips { display: flex; flex-wrap: wrap; gap: 8px; }
.chip { font-size: 13px; padding: 3px 12px; border: 1px solid var(--line); border-radius: 999px; background: var(--sheet); color: var(--muted); }
.chip strong { color: var(--ink); font-weight: 600; }

.sheet { background: var(--sheet); border: 1px solid var(--line); border-radius: 6px; padding: 24px; display: grid; gap: 18px; min-width: 0; }
.sheet-head { border-bottom: 1px solid var(--line); padding-bottom: 12px; display: grid; gap: 2px; }
.sheet-head h2 { font-size: 21px; font-weight: 600; }
.sheet-head p { font-size: 14px; color: var(--muted); }
.note { font-size: 14px; color: var(--muted); max-width: 70ch; }

.scroll { overflow-x: auto; -webkit-overflow-scrolling: touch; }
.scroll svg { display: block; min-width: 760px; width: 100%; height: auto; }
svg text { font-family: var(--font-body); fill: var(--ink); }
svg .t-muted { fill: var(--muted); }
svg .box { fill: var(--sheet); stroke: var(--ink); stroke-width: 1.4; }
svg .box-accent { fill: var(--accent-soft); stroke: var(--accent); stroke-width: 1.6; }
svg .box-file { fill: var(--bg); stroke: var(--muted); stroke-width: 1.2; stroke-dasharray: 4 3; }
svg .wire { fill: none; stroke: var(--ink); stroke-width: 1.4; }
svg .wire-ai { fill: none; stroke: var(--ai); stroke-width: 1.4; stroke-dasharray: 5 4; }
svg .node { fill: var(--ink); }
svg .arrow { fill: var(--ink); }
svg .arrow-ai { fill: var(--ai); }

/* 단계 */
.steps { display: grid; grid-template-columns: repeat(4, 1fr); gap: 12px; }
.step { border: 1px solid var(--line); border-radius: 6px; padding: 14px; display: grid; gap: 6px; align-content: start; min-width: 0; }
.step .n { width: 24px; height: 24px; border-radius: 50%; background: var(--accent); color: var(--sheet); font-size: 13px; font-weight: 700; display: grid; place-items: center; }
.step h3 { font-size: 15.5px; font-weight: 700; }
.step p { font-size: 14px; }

/* 돌려 보기 */
.solver { display: grid; grid-template-columns: 1fr 1.3fr 1fr; gap: 14px; align-items: stretch; }
.col { border: 1px solid var(--line); border-radius: 6px; padding: 14px; display: grid; gap: 8px; align-content: start; min-width: 0; }
.col h3 { font-size: 13px; font-weight: 600; color: var(--muted); letter-spacing: 0.04em; }
.col ul { margin: 0; padding-left: 18px; display: grid; gap: 4px; font-size: 14.5px; }
.core { border: 1.6px solid var(--accent); background: var(--accent-soft); border-radius: 6px; padding: 16px; display: grid; gap: 8px; align-content: center; min-width: 0; }
.core h3 { font-size: 17px; font-weight: 700; }
.core p { font-size: 14.5px; }
.legend { display: flex; flex-wrap: wrap; gap: 10px 18px; font-size: 13.5px; color: var(--muted); }
.legend span { display: inline-flex; align-items: center; gap: 7px; }
.sw-line { width: 26px; height: 0; border-top: 3px solid; display: inline-block; }
.sw-box { width: 18px; height: 12px; border: 1.4px solid var(--ink); display: inline-block; border-radius: 2px; }

/* 회로 */
.units { display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 12px; }
.unit { border: 1px solid var(--line); border-radius: 6px; padding: 14px; display: grid; gap: 6px; align-content: start; min-width: 0; }
.unit h3 { font-size: 15.5px; font-weight: 700; }
.unit .parts { font-size: 13px; color: var(--muted); }
.unit p { font-size: 14px; }

/* AI */
.ai-row { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; }
.ai-card { border: 1.6px solid var(--ai); background: var(--ai-soft); border-radius: 6px; padding: 16px; display: grid; gap: 8px; align-content: start; min-width: 0; }
.ai-card .who { font-size: 12.5px; color: var(--muted); letter-spacing: 0.04em; }
.ai-card h3 { font-size: 16.5px; font-weight: 700; }
.ai-card ul { margin: 0; padding-left: 18px; display: grid; gap: 4px; font-size: 14.5px; }
.more { display: flex; flex-wrap: wrap; justify-content: space-between; align-items: center; gap: 10px; border-top: 1px solid var(--line); padding-top: 14px; font-size: 14.5px; }
.more a { font-weight: 600; text-decoration: none; border: 1.4px solid var(--accent); padding: 6px 14px; border-radius: 4px; }
.more a:hover { background: var(--accent-soft); }

.foot { font-size: 13px; color: var(--muted); }

@media (max-width: 860px) {
  .steps { grid-template-columns: 1fr 1fr; }
}
@media (max-width: 760px) {
  .solver, .ai-row { grid-template-columns: 1fr; }
  .sheet { padding: 18px; }
}
@media (max-width: 440px) {
  .steps { grid-template-columns: 1fr; }
}
.sw-positive { border-color: var(--w-pos); }
.sw-zero { border-color: var(--w-zero); }
.sw-phase-one { border-color: var(--w-ph1); }
.sw-phase-two { border-color: var(--w-ph2); }
.sw-phase-three { border-color: var(--w-ph3); }
.sw-contact { border-color: var(--w-contact); box-shadow: 0 0 0 4px var(--w-contact-halo); }
.sw-coil { background: var(--w-coil); }
.sw-diagnostic { border-color: var(--w-diag); border-width: 2px; }