body {
  font-family: Inter, system-ui, sans-serif;
  background: #f5f7fb;
  color: #111;
  display: flex;
  align-items: center;
  justify-content: center;
  height: 100vh;
  margin: 0;
}

.card {
  background: white;
  border-radius: 12px;
  box-shadow: 0 8px 30px rgba(12, 20, 45, 0.08);
  padding: 22px;
  width: 420px;
}

h1 {
  margin: 0 0 10px;
  font-size: 20px;
}
.target {
  background: #eef6ff;
  padding: 12px;
  border-radius: 8px;
  margin-bottom: 12px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.formula {
  font-weight: 700;
  font-size: 18px;
}
.controls {
  display: flex;
  gap: 8px;
  margin: 12px 0;
  flex-wrap: wrap;
}
.btn {
  padding: 8px 12px;
  border-radius: 8px;
  border: 0;
  cursor: pointer;
  box-shadow: 0 2px 6px rgba(12, 20, 45, 0.06);
}
.elem {
  background: #fff;
  border: 1px solid #e1e6f0;
}
.elem:hover {
  transform: translateY(-2px);
}
.display {
  background: #f7fafc;
  padding: 12px;
  border-radius: 8px;
  min-height: 48px;
  display: flex;
  gap: 8px;
  align-items: center;
  flex-wrap: wrap;
}
.chip {
  background: #fff;
  padding: 6px 10px;
  border-radius: 999px;
  border: 1px solid #e6eef7;
  font-weight: 600;
}
.actions {
  display: flex;
  gap: 8px;
  margin-top: 12px;
}
.danger {
  background: #fff0f0;
  border: 1px solid #ffd6d6;
}
.success {
  background: #f0fff6;
  border: 1px solid #d3ffd8;
}
.small {
  font-size: 13px;
  color: #55607a;
}
footer {
  margin-top: 12px;
  text-align: center;
  font-size: 13px;
  color: #667085;
}