body {
  background-color: #0b0f19;
  color: #ffffff;
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  margin: 0;
  padding: 16px;
}
.top-bar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 14px;
}
.lang-btn {
  background: linear-gradient(90deg, #06b6d4, #8b5cf6);
  border: none;
  color: white;
  padding: 8px 16px;
  border-radius: 20px;
  font-weight: bold;
  font-size: 13px;
  cursor: pointer;
  box-shadow: 0 2px 10px rgba(6, 182, 212, 0.3);
}
.card {
  background: linear-gradient(145deg, #131a2c, #1a2238);
  border: 1px solid #2a3655;
  border-radius: 16px;
  padding: 20px;
  margin-bottom: 16px;
  box-shadow: 0 4px 20px rgba(0, 210, 255, 0.1);
}
h2 {
  margin: 0;
  color: #38bdf8;
  font-size: 20px;
}
label {
  display: block;
  margin-top: 14px;
  margin-bottom: 6px;
  font-size: 14px;
  color: #cbd5e1;
}
select, input {
  width: 100%;
  padding: 12px;
  border-radius: 10px;
  border: 1px solid #334155;
  background-color: #0f172a;
  color: #fff;
  font-size: 15px;
  box-sizing: border-box;
}
.calc-btn {
  width: 100%;
  margin-top: 20px;
  padding: 14px;
  border: none;
  border-radius: 12px;
  background: linear-gradient(90deg, #06b6d4, #6366f1);
  color: white;
  font-size: 16px;
  font-weight: bold;
  cursor: pointer;
}
.result-box {
  margin-top: 18px;
  padding: 15px;
  background-color: #0f172a;
  border-left: 4px solid #06b6d4;
  border-radius: 8px;
  display: none;
}
.result-val {
  font-size: 26px;
  font-weight: bold;
  color: #38bdf8;
  margin: 4px 0;
}
.info-box {
  font-size: 13px;
  color: #94a3b8;
  line-height: 1.6;
}