:root {
  --bg: #eef2f7;
  --card: rgba(255, 255, 255, 0.18);
  --accent: #ffffffd5;
  --muted: #000000;
}

/* Reset */
* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: Inter, system-ui, -apple-system, Segoe UI, Roboto, Arial;
  background: url("background.jpg") center/cover fixed no-repeat;
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  padding: 20px;
  color: var(--muted);
}

/* Wrapper */
.center-card {
  width: 100%;
  max-width: 420px;
}

/* Glass card */
.card {
  background: var(--card);
  backdrop-filter: blur(20px) saturate(180%);
  -webkit-backdrop-filter: blur(20px) saturate(180%);
  border-radius: 24px;
  padding: 26px;
  border: 1px solid rgba(255, 255, 255, 0.45);
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.25);
  animation: fadeIn 0.6s ease;
}

header h1 {
  margin: 0 0 18px;
  color: var(--accent);
  font-size: 1.7rem;
  text-align: center;
  font-weight: 700;
}

/* Form */
label {
  display: flex;
  flex-direction: column;
  gap: 6px;
  font-size: 0.9rem;
}

input {
  width: 100%;
  padding: 12px;
  border-radius: 12px;
  border: 1px solid rgba(255, 255, 255, 0.4);
  background: rgba(255, 255, 255, 0.25);
  backdrop-filter: blur(12px);
  font-size: 1rem;
  transition: 0.25s ease;
}

/* Hover */
input:hover {
  background: rgba(255, 255, 255, 0.45);
}

/* Focus */
input:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(255, 255, 255, 0.25);
}

/* Remove arrows */
input[type=number]::-webkit-inner-spin-button,
input[type=number]::-webkit-outer-spin-button {
  -webkit-appearance: none;
  margin: 0;
}

/* Form grid */
.form-row {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 12px;
  margin-bottom: 16px;
}

/* Button */
.btn {
  padding: 12px;
  border-radius: 14px;
  cursor: pointer;
  border: none;
  font-weight: 600;
  transition: 0.25s;
}

.btn-primary {
  background: var(--accent);
  color: black;
  box-shadow: 0 4px 18px rgba(255, 255, 255, 0.35);
}

.btn-primary:hover {
  transform: translateY(-2px);
}

/* Result card */
.result-card {
  margin-top: 16px;
  padding: 18px;
  background: rgba(255, 255, 255, 0.3);
  border-radius: 16px;
  backdrop-filter: blur(16px);
  animation: fadeIn 0.4s ease;
}

.tips {
  margin-top: 8px;
  font-size: 0.9rem;
  opacity: 0.85;
}

/* Animation */
@keyframes fadeIn {
  from {
    opacity: 0;
    transform: translateY(6px);
  }

  to {
    opacity: 1;
    transform: translateY(0);
  }
}