:root {
  --bg-main: #06130c;
  --bg-panel: #0d2217;
  --bg-panel-soft: #123023;
  --line: #2f5f49;
  --text-main: #e8f7ee;
  --text-soft: #c5e7d2;
  --accent: #61d48f;
  --accent-strong: #89ffb5;
  --warn: #f6cb6f;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
  background: radial-gradient(circle at top left, #133828 0%, var(--bg-main) 55%);
  color: var(--text-main);
}

.app-shell {
  width: 100%;
  margin: 0;
  padding: 1.25rem;
  display: grid;
  grid-template-columns: 1fr 2fr;
  gap: 1.2rem;
}

.panel {
  background: linear-gradient(150deg, var(--bg-panel) 0%, #0b1c13 100%);
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 1.2rem;
  box-shadow: 0 12px 24px rgba(0, 0, 0, 0.2);
}

h1,
h2 {
  margin-top: 0;
  margin-bottom: 0.55rem;
  line-height: 1.2;
}

h1 {
  font-size: 1.5rem;
}

h2 {
  font-size: 1.3rem;
}

.hint {
  margin-top: 0;
  margin-bottom: 1rem;
  color: var(--text-soft);
}

table {
  width: 100%;
  border-collapse: collapse;
  border-radius: 10px;
  overflow: hidden;
}

thead th {
  text-align: left;
  font-weight: 600;
  padding: 0.7rem;
  background: #19412f;
}

tbody td {
  padding: 0.62rem 0.7rem;
  border-top: 1px solid #1f4a35;
  background: #10271b;
}

tbody tr:nth-child(even) td {
  background: #0e2418;
}

.status {
  margin: 1rem 0 0;
  padding: 0.65rem 0.75rem;
  border-radius: 8px;
  background: var(--bg-panel-soft);
  border: 1px solid #2c664d;
}

.status.balanced {
  border-color: var(--accent);
  color: var(--accent-strong);
}

.status.not-balanced {
  color: var(--warn);
}

.status.not-simplest {
  border-color: #b69242;
  color: var(--warn);
}

.reaction-panel {
  display: flex;
  flex-direction: column;
  justify-content: flex-start;
  min-width: 0;
}

.reaction-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.9rem;
}

.reaction-actions {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
}

.new-reaction-btn {
  border: 1px solid #3f7e61;
  border-radius: 8px;
  background: #163927;
  color: var(--text-main);
  font-size: 0.92rem;
  font-weight: 600;
  padding: 0.48rem 0.72rem;
  cursor: pointer;
}

.new-reaction-btn:hover {
  background: #1c4a32;
}

.new-reaction-btn:focus {
  outline: 2px solid var(--accent);
  outline-offset: 1px;
  border-color: var(--accent);
}

.clear-btn {
  background: #103222;
}

.clear-btn:hover {
  background: #16412d;
}

.reaction-meta {
  margin-top: 0;
  margin-bottom: 0.8rem;
}

.sum-panel {
  grid-column: 1 / -1;
}

.sum-grid {
  display: grid;
  grid-template-columns: auto minmax(7rem, 14rem);
  align-items: center;
  gap: 0.75rem 1rem;
  margin-top: 0.8rem;
}

.sum-input {
  width: 100%;
  max-width: 100%;
  padding: 0.45rem 0.5rem;
  border: 1px solid #3e7a5d;
  border-radius: 6px;
  background: #0a1a12;
  color: var(--text-main);
  text-align: center;
  font-size: 1rem;
}

.sum-input:focus {
  outline: 2px solid var(--accent);
  outline-offset: 1px;
  border-color: var(--accent);
}

[hidden] {
  display: none !important;
}

.reaction {
  display: flex;
  flex-wrap: nowrap;
  align-items: center;
  gap: 0.55rem;
  font-size: 1.4rem;
  line-height: 1.2;
  white-space: nowrap;
  overflow-x: auto;
  background: #0f271b;
  border: 1px solid #27523d;
  border-radius: 10px;
  padding: 1rem;
}

.coeff {
  display: inline-flex;
  align-items: center;
}

.coefficient {
  width: 3rem;
  padding: 0.4rem 0.2rem;
  border: 1px solid #3e7a5d;
  border-radius: 6px;
  background: #0a1a12;
  color: var(--text-main);
  text-align: center;
  font-size: 1rem;
}

.coefficient:focus {
  outline: 2px solid var(--accent);
  outline-offset: 1px;
  border-color: var(--accent);
}

.formula {
  font-weight: 600;
}

.operator {
  color: #9ddcb9;
  font-weight: 600;
  margin: 0 0.1rem;
}

.arrow {
  margin: 0 0.35rem;
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

@media (max-width: 860px) {
  .app-shell {
    grid-template-columns: 1fr;
  }

  .reaction-header {
    flex-wrap: wrap;
  }

  .reaction-actions {
    width: 100%;
    justify-content: flex-end;
    flex-wrap: wrap;
  }

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

  .reaction {
    font-size: 1.25rem;
  }
}