:root {
  --bg: #0c1118;
  --panel: #121a23;
  --panel-border: #243140;
  --text: #edf2f7;
  --muted: #9fb0c3;
  --accent: #2dc7b8;
  --accent-soft: #1d6f77;
  --alert: #ff7a6d;
  --ok: #f7b846;
  --radius: 16px;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Plus Jakarta Sans", "Pretendard", "Apple SD Gothic Neo", sans-serif;
  background: radial-gradient(1200px 700px at 5% -10%, #193149 0%, transparent 45%),
    radial-gradient(800px 600px at 100% 0%, #1c3b2d 0%, transparent 40%),
    var(--bg);
  color: var(--text);
  min-height: 100vh;
}

.bg-grid {
  position: fixed;
  inset: 0;
  z-index: -1;
  background-image: linear-gradient(rgba(180, 196, 212, 0.05) 1px, transparent 1px),
    linear-gradient(90deg, rgba(180, 196, 212, 0.05) 1px, transparent 1px);
  background-size: 26px 26px;
  mask-image: radial-gradient(ellipse at center, black 35%, transparent 90%);
}

.app-shell {
  width: min(1180px, 94vw);
  margin: 2.2rem auto 3rem;
  display: grid;
  gap: 1rem;
}

.app-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-end;
  gap: 1rem;
  padding: 1.2rem 1.4rem;
  background: color-mix(in srgb, var(--panel) 90%, black);
  border: 1px solid var(--panel-border);
  border-radius: var(--radius);
}

h1,
h2 {
  margin: 0;
}

h1 {
  font-size: clamp(1.25rem, 2vw, 1.8rem);
}

h2 {
  font-size: 1rem;
  margin-bottom: 0.8rem;
}

.subtext {
  margin: 0.45rem 0 0;
  color: var(--muted);
  font-size: 0.92rem;
}

.header-actions {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
}

.stat-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 0.8rem;
}

.stat-card {
  padding: 1rem;
  border-radius: var(--radius);
  border: 1px solid var(--panel-border);
  background: var(--panel);
  min-height: 105px;
}

.stat-card.emphasis {
  background: linear-gradient(145deg, #15343e, #102a31);
}

.stat-label {
  margin: 0;
  color: var(--muted);
  font-size: 0.83rem;
}

.stat-value {
  margin: 0.35rem 0 0;
  font-weight: 700;
  font-size: clamp(1.1rem, 2.4vw, 1.55rem);
}

.content-grid {
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: 0.8rem;
}

.panel {
  background: var(--panel);
  border: 1px solid var(--panel-border);
  border-radius: var(--radius);
  padding: 1rem;
}

.field-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.7rem;
}

.field {
  display: grid;
  gap: 0.35rem;
}

.field span {
  font-size: 0.84rem;
  color: var(--muted);
}

input,
button {
  font: inherit;
}

input[type="number"],
input[type="text"],
input[type="range"] {
  width: 100%;
}

input[type="number"],
input[type="text"] {
  border-radius: 10px;
  border: 1px solid #2a3c4e;
  background: #0f151c;
  color: var(--text);
  padding: 0.58rem 0.62rem;
}

input[type="range"] {
  accent-color: var(--accent);
}

.actions {
  margin-top: 0.9rem;
  display: flex;
  gap: 0.5rem;
}

button {
  border: 0;
  border-radius: 10px;
  padding: 0.58rem 0.82rem;
  background: var(--accent);
  color: #032a2b;
  font-weight: 700;
  cursor: pointer;
}

button.ghost {
  background: transparent;
  color: var(--text);
  border: 1px solid #32536a;
}

button:hover {
  filter: brightness(1.04);
}

.error {
  min-height: 1.2em;
  color: var(--alert);
  margin: 0.55rem 0 0;
  font-size: 0.9rem;
}

.result-list {
  margin: 0;
  display: grid;
  gap: 0.55rem;
}

.result-list div {
  display: flex;
  justify-content: space-between;
  gap: 0.6rem;
  border-bottom: 1px dashed #2b3d4d;
  padding-bottom: 0.35rem;
}

.result-list dt {
  color: var(--muted);
  font-size: 0.87rem;
}

.result-list dd {
  margin: 0;
  font-weight: 700;
}

.explain-box {
  margin-top: 0.8rem;
  padding: 0.75rem;
  border-radius: 12px;
  border: 1px solid #305474;
  background: #0d1d2b;
}

.explain-title {
  margin: 0;
  font-size: 0.9rem;
  font-weight: 700;
}

.explain-list {
  margin: 0.5rem 0 0;
  padding-left: 1rem;
  display: grid;
  gap: 0.32rem;
  color: var(--muted);
  font-size: 0.88rem;
}

.explain-note {
  margin: 0.5rem 0 0;
  color: #c7d6e6;
  font-size: 0.85rem;
}

.info-box,
.warning-box {
  margin: 0.85rem 0 0;
  padding: 0.7rem;
  border-radius: 12px;
  font-size: 0.9rem;
}

.info-box {
  background: #0e2231;
  border: 1px solid #295274;
}

.warning-box {
  background: #322113;
  border: 1px solid #9c5d1b;
}

.hidden {
  display: none;
}

.chart-panel .chart-wrap {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.donut {
  width: 140px;
  height: 140px;
  border-radius: 50%;
  position: relative;
  background: conic-gradient(var(--accent) 0deg, var(--accent-soft) 0deg 360deg);
}

.donut::after {
  content: "";
  position: absolute;
  inset: 22px;
  border-radius: 50%;
  background: #101823;
  border: 1px solid #294152;
}

.legend {
  display: grid;
  gap: 0.35rem;
  font-size: 0.9rem;
}

.legend p {
  margin: 0;
  color: var(--muted);
}

.dot {
  display: inline-block;
  width: 10px;
  height: 10px;
  border-radius: 50%;
  margin-right: 0.25rem;
}

.dot.fixed {
  background: var(--accent);
}

.dot.variable {
  background: var(--accent-soft);
}

.simulation-result {
  margin-top: 0.8rem;
  display: grid;
  gap: 0.35rem;
}

.simulation-result p {
  margin: 0;
  color: var(--muted);
}

.simulation-result strong {
  color: var(--text);
}

.example-list {
  margin: 0;
  padding-left: 1.2rem;
  display: grid;
  gap: 0.45rem;
  color: var(--muted);
}

@media (max-width: 980px) {
  .stat-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .content-grid {
    grid-template-columns: 1fr;
  }

  .app-header {
    align-items: flex-start;
    flex-direction: column;
  }
}

@media (max-width: 640px) {
  .field-grid {
    grid-template-columns: 1fr;
  }

  .stat-grid {
    grid-template-columns: 1fr;
  }

  .donut {
    width: 120px;
    height: 120px;
  }

  .donut::after {
    inset: 20px;
  }
}