:root{
  --bg: #070912;
  --panel: rgba(10, 14, 28, 0.72);
  --panel-2: rgba(16, 22, 40, 0.85);
  --border: rgba(127, 255, 233, 0.18);
  --text: #eaf7ff;
  --muted: rgba(234, 247, 255, 0.72);
  --cyan: #00f5ff;
  --pink: #ff3df2;
  --violet: #8d6bff;
  --green: #5dff9a;
  --yellow: #ffd65c;
  --danger: #ff5d7a;
  --shadow: 0 0 18px rgba(0, 245, 255, 0.12), 0 0 40px rgba(141, 107, 255, 0.12);
  --radius: 20px;
  --radius-sm: 14px;
  --max: 1200px;
}

*{ box-sizing: border-box; }
html{ scroll-behavior: smooth; }
body{
  margin:0;
  font-family: Inter, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background:
    radial-gradient(circle at 10% 10%, rgba(255,61,242,.16), transparent 24%),
    radial-gradient(circle at 90% 20%, rgba(0,245,255,.14), transparent 22%),
    radial-gradient(circle at 50% 100%, rgba(141,107,255,.18), transparent 30%),
    linear-gradient(180deg, #05060b 0%, #070912 45%, #06070e 100%);
  color: var(--text);
  min-height: 100vh;
  overflow-x: hidden;
}

.bg-grid{
  position: fixed;
  inset: 0;
  pointer-events: none;
  background-image:
    linear-gradient(rgba(255,255,255,.03) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255,255,255,.03) 1px, transparent 1px);
  background-size: 44px 44px;
  mask-image: linear-gradient(180deg, rgba(0,0,0,.9), transparent 95%);
  opacity: .35;
}

.bg-orb{
  position: fixed;
  border-radius: 50%;
  filter: blur(18px);
  pointer-events:none;
  opacity: .65;
}
.bg-orb-1{
  width: 260px; height: 260px;
  background: radial-gradient(circle, rgba(0,245,255,.25), rgba(0,245,255,0));
  top: -80px; right: -50px;
}
.bg-orb-2{
  width: 320px; height: 320px;
  background: radial-gradient(circle, rgba(255,61,242,.2), rgba(255,61,242,0));
  bottom: -120px; left: -70px;
}

.hero, .app-shell, .footer{
  width: min(var(--max), calc(100% - 24px));
  margin-inline: auto;
}

.hero{
  padding: 28px 0 18px;
  position: relative;
  z-index: 1;
}

.hero__brand{
  display:flex;
  align-items:center;
  gap:16px;
  flex-wrap: wrap;
}

.logo-mark{
  width: 58px;
  height: 58px;
  border-radius: 18px;
  display:grid;
  place-items:center;
  font-weight: 900;
  letter-spacing: .08em;
  color: #040712;
  background: linear-gradient(135deg, var(--cyan), var(--pink));
  box-shadow: 0 0 20px rgba(0,245,255,.35), 0 0 30px rgba(255,61,242,.25);
}

.eyebrow{
  margin:0 0 6px;
  color: var(--cyan);
  text-transform: uppercase;
  letter-spacing: .18em;
  font-size: .78rem;
}

h1{
  margin:0;
  font-size: clamp(2rem, 4vw, 3.5rem);
  line-height: 1;
  letter-spacing: -0.04em;
  text-shadow: 0 0 18px rgba(0,245,255,.15);
}

.subtitle{
  margin: 10px 0 0;
  color: var(--muted);
  max-width: 62ch;
}

.hero__chips{
  display:flex;
  gap:10px;
  flex-wrap: wrap;
  margin-top: 18px;
}

.chip, .status-chip{
  display:inline-flex;
  align-items:center;
  gap:8px;
  border: 1px solid var(--border);
  background: rgba(5, 9, 18, .55);
  color: var(--text);
  padding: 8px 12px;
  border-radius: 999px;
  font-size: .9rem;
  box-shadow: var(--shadow);
  backdrop-filter: blur(10px);
}

.status-chip--soft{
  color: var(--muted);
}

.app-shell{
  display:grid;
  grid-template-columns: 1.05fr .95fr;
  gap: 18px;
  padding: 10px 0 24px;
  position: relative;
  z-index: 1;
}

.panel{
  border: 1px solid var(--border);
  background: linear-gradient(180deg, rgba(12, 16, 30, .82), rgba(8, 12, 22, .76));
  border-radius: var(--radius);
  padding: 18px;
  box-shadow: var(--shadow);
  backdrop-filter: blur(16px);
  overflow: hidden;
}

.panel::before{
  content:"";
  position:absolute;
  inset: 0;
  pointer-events:none;
  background: linear-gradient(135deg, rgba(0,245,255,.08), transparent 25%, transparent 75%, rgba(255,61,242,.08));
  opacity: .65;
}

.panel > *{ position: relative; z-index: 1; }

.panel__header h2{
  margin:0;
  font-size: clamp(1.1rem, 2vw, 1.5rem);
}
.panel__header p{
  margin: 6px 0 0;
  color: var(--muted);
}

.panel--form, .panel--graph, .panel--about, .panel--faq, .panel--history{
  grid-column: span 1;
}
.panel--form{ min-height: 100%; }
.panel--result{ grid-row: span 2; }

.equation-preview{
  margin: 16px 0 16px;
  padding: 14px 16px;
  border-radius: 16px;
  background: linear-gradient(90deg, rgba(0,245,255,.08), rgba(255,61,242,.08));
  border: 1px solid rgba(255,255,255,.08);
  font-size: clamp(1rem, 2.2vw, 1.25rem);
  font-weight: 700;
  letter-spacing: .03em;
  overflow-x:auto;
}

.solver-form{
  display:flex;
  flex-direction: column;
  gap: 14px;
}

.grid-3{
  display:grid;
  grid-template-columns: repeat(3, minmax(0,1fr));
  gap: 12px;
}

.field{
  display:flex;
  flex-direction: column;
  gap: 8px;
}
.field span{
  color: var(--muted);
  font-size: .92rem;
}

input, select{
  width: 100%;
  appearance: none;
  border: 1px solid rgba(0,245,255,.22);
  background: rgba(5, 10, 20, .82);
  color: var(--text);
  border-radius: 14px;
  padding: 14px 14px;
  font-size: 1rem;
  outline: none;
  transition: .2s ease;
  box-shadow: inset 0 0 0 1px rgba(255,255,255,0.02);
}
input:focus, select:focus{
  border-color: rgba(0,245,255,.6);
  box-shadow: 0 0 0 4px rgba(0,245,255,.12);
}

.actions, .mini-actions{
  display:flex;
  flex-wrap: wrap;
  gap: 10px;
}

.btn, .link-btn{
  border: 1px solid rgba(255,255,255,.12);
  background: rgba(8, 14, 28, .86);
  color: var(--text);
  border-radius: 14px;
  cursor:pointer;
  transition: transform .16s ease, border-color .16s ease, box-shadow .16s ease, background .16s ease;
  padding: 12px 14px;
  font-weight: 700;
}
.btn:hover, .link-btn:hover{
  transform: translateY(-1px);
  border-color: rgba(0,245,255,.35);
  box-shadow: 0 0 0 4px rgba(0,245,255,.08);
}
.btn--primary{
  background: linear-gradient(135deg, rgba(0,245,255,.92), rgba(255,61,242,.92));
  color: #05060b;
  border-color: transparent;
}
.link-btn{
  padding: 10px 12px;
  color: var(--cyan);
  background: transparent;
}

.status-row{
  display:flex;
  gap:10px;
  flex-wrap: wrap;
  margin: 10px 0 14px;
}

.result-box{
  min-height: 170px;
  padding: 16px;
  border-radius: 16px;
  border: 1px solid rgba(255,255,255,.08);
  background: rgba(4, 8, 16, .68);
}

.result-box h3{
  margin:0 0 10px;
  font-size: 1.1rem;
}
.result-box p, .result-box li{
  color: var(--text);
}
.muted{ color: var(--muted); }
.result-list{
  margin: 12px 0 0;
  padding-left: 18px;
}
.result-list li{
  margin: 8px 0;
  color: var(--muted);
}

.method-card{
  margin-top: 14px;
  border: 1px solid rgba(255,255,255,.08);
  border-radius: 16px;
  padding: 14px;
  background: rgba(8, 12, 22, .7);
}
.method-card h4{
  margin: 0 0 8px;
}
.method-card ol{
  margin: 0;
  padding-left: 18px;
}
.method-card li{
  margin: 8px 0;
  color: var(--muted);
}

.metrics-grid{
  display:grid;
  grid-template-columns: repeat(2, minmax(0,1fr));
  gap: 12px;
  margin-top: 14px;
}
.metric{
  border-radius: 16px;
  padding: 14px;
  border: 1px solid rgba(255,255,255,.08);
  background: rgba(8, 12, 22, .68);
}
.metric .label{
  color: var(--muted);
  font-size: .88rem;
}
.metric .value{
  margin-top: 8px;
  font-size: 1.06rem;
  font-weight: 800;
}

.graph-wrap{
  border-radius: 18px;
  overflow: hidden;
  border: 1px solid rgba(255,255,255,.08);
  background:
    linear-gradient(180deg, rgba(3, 8, 18, .9), rgba(7, 12, 24, .85));
}
canvas{
  display:block;
  width: 100%;
  height: auto;
  aspect-ratio: 900 / 520;
}

.graph-note{
  color: var(--muted);
  margin: 10px 0 0;
  font-size: .92rem;
}

.history-list{
  display:grid;
  grid-template-columns: 1fr;
  gap: 10px;
}
.history-item{
  border: 1px solid rgba(255,255,255,.08);
  border-radius: 16px;
  padding: 12px 14px;
  background: rgba(8, 12, 22, .68);
  display:flex;
  justify-content: space-between;
  gap: 12px;
  align-items:center;
}
.history-item strong{
  display:block;
  margin-bottom: 4px;
}
.history-item small{
  color: var(--muted);
}
.history-item button{
  white-space: nowrap;
}

.about-text p{
  margin: 0 0 12px;
  color: var(--muted);
  line-height: 1.65;
}

.faq{
  display:grid;
  gap: 10px;
}
details{
  border: 1px solid rgba(255,255,255,.08);
  border-radius: 16px;
  background: rgba(8, 12, 22, .68);
  padding: 12px 14px;
}
summary{
  cursor:pointer;
  font-weight: 700;
  color: var(--text);
}
details p{
  color: var(--muted);
  line-height: 1.6;
  margin: 10px 0 0;
}

.footer{
  padding: 8px 0 28px;
  color: var(--muted);
  text-align:center;
  position: relative;
  z-index: 1;
}

.toast{
  position: fixed;
  left: 50%;
  bottom: 18px;
  transform: translateX(-50%) translateY(20px);
  background: rgba(8, 12, 22, .95);
  color: var(--text);
  border: 1px solid rgba(0,245,255,.25);
  padding: 12px 14px;
  border-radius: 14px;
  box-shadow: var(--shadow);
  opacity: 0;
  pointer-events:none;
  transition: .25s ease;
  max-width: min(92vw, 420px);
  z-index: 99;
}
.toast.show{
  opacity: 1;
  transform: translateX(-50%) translateY(0);
}

@media (max-width: 980px){
  .app-shell{
    grid-template-columns: 1fr;
  }
  .panel--result{
    grid-row: auto;
  }
}

@media (max-width: 720px){
  .hero{
    padding-top: 18px;
  }
  .grid-3{
    grid-template-columns: 1fr;
  }
  .metrics-grid{
    grid-template-columns: 1fr;
  }
  .actions, .mini-actions{
    flex-direction: column;
  }
  .btn, .link-btn{
    width: 100%;
    justify-content:center;
  }
  .history-item{
    flex-direction: column;
    align-items: stretch;
  }
}