@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;600&display=swap');

:root {
  --color-bg: #0F172A;
  --color-accent: #22D3EE;
  --color-white: #F8FAFC;
  --color-muted: #94A3B8;
  --font-ui: 'Inter', sans-serif;
  --border-radius: 1rem;
  --transition: 0.3s ease;
}

body {
  margin: 0;
  background: var(--color-bg);
  color: var(--color-white);
  font-family: var(--font-ui);
  min-height: 100vh;
  display: flex;
  justify-content: center;
  padding: 20px 12px;
}

.app-container {
  max-width: 900px;
  width: 100%;
  display: flex;
  flex-direction: column;
  gap: 32px;
}

header {
  text-align: center;
}

header h1 {
  font-weight: 600;
  font-size: 2.4rem;
  color: var(--color-accent);
  margin-bottom: 6px;
  text-shadow: 0 0 6px var(--color-accent);
}

header .subtitle {
  font-weight: 400;
  font-size: 1.1rem;
  color: var(--color-muted);
}

.input-section {
  background: #1E293B;
  border-radius: var(--border-radius);
  padding: 24px 28px;
  box-shadow: 0 0 16px var(--color-accent);
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.input-label {
  font-weight: 600;
  font-size: 1.1rem;
  color: var(--color-accent);
}

textarea#expr-input {
  font-family: 'JetBrains Mono', monospace;
  font-size: 1.15rem;
  padding: 14px 18px;
  border-radius: var(--border-radius);
  border: none;
  background: #334155;
  color: var(--color-white);
  resize: vertical;
  min-height: 70px;
  box-shadow: inset 0 0 8px #0ff1ff55;
  transition: box-shadow var(--transition);
}

textarea#expr-input:focus {
  outline: none;
  box-shadow: 0 0 12px var(--color-accent);
}

.mode-tabs {
  display: flex;
  gap: 12px;
  margin-top: 12px;
  flex-wrap: wrap;
}

.tab-btn {
  flex: 1 1 auto;
  background: transparent;
  border: 2px solid var(--color-accent);
  color: var(--color-accent);
  font-weight: 600;
  font-size: 1rem;
  padding: 10px 14px;
  border-radius: var(--border-radius);
  cursor: pointer;
  transition: background var(--transition), color var(--transition), box-shadow var(--transition);
}

.tab-btn.active,
.tab-btn:focus {
  background: var(--color-accent);
  color: var(--color-bg);
  box-shadow: 0 0 12px var(--color-accent);
  outline: none;
}

.btn-solve {
  margin-top: 18px;
  background: var(--color-accent);
  border: none;
  color: var(--color-bg);
  font-weight: 700;
  font-family: 'JetBrains Mono', monospace;
  font-size: 1.2rem;
  padding: 14px 0;
  border-radius: var(--border-radius);
  cursor: pointer;
  letter-spacing: 1.5px;
  box-shadow: 0 0 20px var(--color-accent);
  transition: background 0.3s ease;
}

.btn-solve:hover,
.btn-solve:focus {
  background: #0bc9d8;
  box-shadow: 0 0 28px #0bc9d8;
  outline: none;
}

.output-section {
  background: #1E293B;
  border-radius: var(--border-radius);
  padding: 24px 28px;
  box-shadow: 0 0 16px var(--color-accent);
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.output-section h2 {
  font-weight: 600;
  font-size: 1.7rem;
  color: var(--color-accent);
}

.output-tabs {
  display: flex;
  gap: 14px;
  flex-wrap: wrap;
}

.output-tab {
  flex: 1 1 auto;
  background: transparent;
  border: 2px solid var(--color-accent);
  color: var(--color-accent);
  font-weight: 600;
  font-size: 1rem;
  padding: 10px 14px;
  border-radius: var(--border-radius);
  cursor: pointer;
  transition: background var(--transition), color var(--transition), box-shadow var(--transition);
}

.output-tab.active,
.output-tab:focus {
  background: var(--color-accent);
  color: var(--color-bg);
  box-shadow: 0 0 12px var(--color-accent);
  outline: none;
}

.output-panel {
  background: #0F172A;
  border-radius: var(--border-radius);
  padding: 18px 22px;
  color: var(--color-white);
  font-family: 'JetBrains Mono', monospace;
  font-size: 1.1rem;
  min-height: 160px;
  overflow-y: auto;
  display: none;
  white-space: pre-wrap;
  user-select: text;
}

.output-panel.active {
  display: block;
}

#plotly-graph {
  width: 100%;
  height: 350px;
  border-radius: var(--border-radius);
  box-shadow: inset 0 0 14px var(--color-accent);
  user-select: none;
}

/* Responsive */
@media (max-width: 720px) {
  .mode-tabs, .output-tabs {
    flex-wrap: wrap;
  }
}