:root {
  --primary: #1976D2;
  --primary-dark: #1565C0;
  --primary-light: #BBDEFB;
  --error: #D32F2F;
  --error-light: #FFCDD2;
  --surface: #FFFFFF;
  --background: #F0F2F5;
  --text-primary: #212121;
  --text-secondary: #5F6368;
  --text-hint: #9AA0A6;
  --text-on-primary: #FFFFFF;
  --border: #DADCE0;
  --radius: 12px;
  --radius-sm: 8px;
  --radius-xs: 4px;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.08), 0 1px 2px rgba(0,0,0,0.06);
  --shadow-md: 0 4px 6px rgba(0,0,0,0.07), 0 2px 4px rgba(0,0,0,0.06);
  --shadow-lg: 0 10px 25px rgba(0,0,0,0.1), 0 4px 10px rgba(0,0,0,0.06);
  --spacing-xs: 4px;
  --spacing-sm: 8px;
  --spacing-md: 16px;
  --spacing-lg: 24px;
  --spacing-xl: 32px;
  --touch-target: 48px;
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html { font-size: 16px; -webkit-text-size-adjust: 100%; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  background: var(--background);
  color: var(--text-primary);
  line-height: 1.5;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
}

h1 { font-size: 1.5rem; font-weight: 500; letter-spacing: -0.01em; }
h2 { font-size: 1.125rem; font-weight: 500; margin-bottom: var(--spacing-md); color: var(--text-primary); }
h3 { font-size: 0.875rem; font-weight: 500; text-transform: uppercase; letter-spacing: 0.05em; color: var(--text-secondary); margin-bottom: var(--spacing-sm); }

p { color: var(--text-secondary); font-size: 0.9375rem; }

#app {
  max-width: 640px;
  margin: 0 auto;
  padding: var(--spacing-md);
  padding-bottom: calc(var(--spacing-xl) * 2);
}

header {
  text-align: center;
  padding: var(--spacing-xl) var(--spacing-md) var(--spacing-lg);
}

header h1 {
  font-size: 1.75rem;
  font-weight: 600;
  color: var(--primary);
  margin-bottom: var(--spacing-xs);
}

header p {
  font-size: 0.9375rem;
  color: var(--text-secondary);
  max-width: 400px;
  margin: 0 auto;
}

.card {
  background: var(--surface);
  border-radius: var(--radius);
  padding: var(--spacing-lg);
  margin-bottom: var(--spacing-md);
  box-shadow: var(--shadow-sm);
  transition: box-shadow 0.2s;
}

.card-title {
  font-size: 1rem;
  font-weight: 500;
  margin-bottom: var(--spacing-md);
  color: var(--text-primary);
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
}

.card-title .step {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 24px;
  height: 24px;
  border-radius: 50%;
  background: var(--primary);
  color: var(--text-on-primary);
  font-size: 0.75rem;
  font-weight: 600;
  flex-shrink: 0;
}

.form-group {
  margin-bottom: var(--spacing-md);
}

.form-group:last-child { margin-bottom: 0; }

.form-label {
  display: block;
  font-size: 0.8125rem;
  font-weight: 500;
  color: var(--text-secondary);
  margin-bottom: var(--spacing-sm);
}

.radio-group {
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-sm);
}

.radio-option {
  position: relative;
  flex: 1 1 auto;
  min-width: 0;
}

.radio-option input[type="radio"] {
  position: absolute;
  opacity: 0;
  width: 0;
  height: 0;
  pointer-events: none;
}

.radio-option label {
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 0.625rem 1rem;
  border: 2px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-secondary);
  cursor: pointer;
  transition: all 0.2s;
  text-align: center;
  min-height: var(--touch-target);
  user-select: none;
  -webkit-tap-highlight-color: transparent;
}

.radio-option input[type="radio"]:checked + label {
  border-color: var(--primary);
  background: var(--primary-light);
  color: var(--primary-dark);
}

.radio-option label:hover {
  border-color: var(--primary);
  background: #F0F6FF;
}

.radio-option input[type="radio"]:focus-visible + label {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}

select, input[type="number"], input[type="text"] {
  width: 100%;
  padding: 0.75rem 1rem;
  border: 2px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: 0.9375rem;
  font-family: inherit;
  color: var(--text-primary);
  background: var(--surface);
  transition: border-color 0.2s;
  min-height: var(--touch-target);
  appearance: none;
  -webkit-appearance: none;
}

select {
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='8' viewBox='0 0 12 8'%3E%3Cpath d='M1 1l5 5 5-5' stroke='%235F6368' stroke-width='2' fill='none' stroke-linecap='round'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 1rem center;
  padding-right: 2.5rem;
}

select:focus, input[type="number"]:focus, input[type="text"]:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(25,118,210,0.12);
}

select:hover, input[type="number"]:hover, input[type="text"]:hover {
  border-color: #B0B0B0;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-sm);
  padding: 0.75rem 1.5rem;
  border: none;
  border-radius: var(--radius-sm);
  font-family: inherit;
  font-size: 0.9375rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
  min-height: var(--touch-target);
  min-width: var(--touch-target);
  user-select: none;
  -webkit-tap-highlight-color: transparent;
  text-decoration: none;
  letter-spacing: 0.01em;
}

.btn-primary {
  background: var(--primary);
  color: var(--text-on-primary);
  box-shadow: var(--shadow-sm);
  width: 100%;
}

.btn-primary:hover {
  background: var(--primary-dark);
  box-shadow: var(--shadow-md);
}

.btn-primary:active {
  transform: scale(0.98);
}

.btn-primary:focus-visible {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}

.btn-outline {
  background: var(--surface);
  border: 2px solid var(--border);
  color: var(--text-secondary);
}

.btn-outline:hover {
  border-color: var(--primary);
  color: var(--primary);
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none;
}

.result-card {
  border-top: 4px solid var(--primary);
}

.bac-value {
  font-size: 2.5rem;
  font-weight: 700;
  color: var(--primary);
  text-align: center;
  padding: var(--spacing-md) 0;
}

.bac-value.danger { color: var(--error); }
.bac-value.warning { color: #F57F17; }
.bac-value.safe { color: #2E7D32; }

.bac-label {
  text-align: center;
  font-size: 0.8125rem;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.drink-table {
  width: 100%;
  border-collapse: collapse;
  margin-top: var(--spacing-md);
}

.drink-table th {
  text-align: left;
  font-size: 0.75rem;
  color: var(--text-hint);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  padding: var(--spacing-sm) var(--spacing-xs);
  border-bottom: 2px solid var(--border);
}

.drink-table td {
  padding: var(--spacing-sm) var(--spacing-xs);
  border-bottom: 1px solid var(--border);
  font-size: 0.875rem;
}

.drink-table tr:last-child td { border-bottom: none; }

.toast {
  position: fixed;
  bottom: var(--spacing-lg);
  left: 50%;
  transform: translateX(-50%);
  background: #323232;
  color: #fff;
  padding: 0.875rem 1.5rem;
  border-radius: var(--radius-sm);
  font-size: 0.875rem;
  font-weight: 500;
  box-shadow: var(--shadow-lg);
  z-index: 1000;
  max-width: 90vw;
  text-align: center;
  transition: opacity 0.3s, transform 0.3s;
  opacity: 0;
  pointer-events: none;
}

.toast.show {
  opacity: 1;
  pointer-events: auto;
}

.toast.error {
  background: var(--error);
}

.spinner {
  display: none;
  width: 20px;
  height: 20px;
  border: 2px solid rgba(255,255,255,0.3);
  border-top-color: #fff;
  border-radius: 50%;
  animation: spin 0.6s linear infinite;
}

.btn.loading .spinner { display: inline-block; }
.btn.loading .btn-text { display: none; }

@keyframes spin { to { transform: rotate(360deg); } }

.hidden { display: none !important; }

/* ---------------------------------------------------------- Stepper */
.stepper {
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: var(--spacing-lg);
  padding: 0 var(--spacing-sm);
}

.stepper-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--spacing-xs);
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
}

.stepper-circle {
  width: 32px;
  height: 32px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.8125rem;
  font-weight: 700;
  border: 2px solid var(--border);
  color: var(--text-hint);
  background: var(--surface);
  transition: all 0.3s;
  flex-shrink: 0;
}

.stepper-item.active .stepper-circle {
  border-color: var(--primary);
  background: var(--primary);
  color: var(--text-on-primary);
}

.stepper-item.completed .stepper-circle {
  border-color: var(--primary);
  background: var(--primary);
  color: var(--text-on-primary);
}

.stepper-label {
  font-size: 0.625rem;
  color: var(--text-hint);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  white-space: nowrap;
  transition: color 0.3s;
}

.stepper-item.active .stepper-label {
  color: var(--primary);
  font-weight: 600;
}

.stepper-item.completed .stepper-label {
  color: var(--text-secondary);
}

.stepper-line {
  flex: 1;
  height: 2px;
  background: var(--border);
  margin: 0 var(--spacing-xs);
  margin-bottom: 18px;
  min-width: 8px;
  transition: background 0.3s;
}

.stepper-line.completed {
  background: var(--primary);
}

/* ---------------------------------------------------------- Steps */
.step {
  display: none;
  animation: stepFadeIn 0.3s ease;
}

.step.active {
  display: block;
}

@keyframes stepFadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to   { opacity: 1; transform: translateY(0); }
}

.step-nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: var(--spacing-sm);
  margin-top: var(--spacing-lg);
  padding-top: var(--spacing-md);
  border-top: 1px solid var(--border);
}

.step-nav .btn {
  flex: 1;
}

.step-nav .btn-outline {
  flex: 0 1 auto;
  min-width: 120px;
}

@media (max-width: 480px) {
  .stepper-circle { width: 28px; height: 28px; font-size: 0.75rem; }
  .stepper-label { font-size: 0.5rem; }
  .stepper-line { margin-bottom: 16px; }
  .step-nav { flex-direction: row; }
  .step-nav .btn-outline { min-width: 100px; }
}

@media (max-width: 480px) {
  #app { padding: var(--spacing-sm); }
  header { padding: var(--spacing-lg) var(--spacing-sm); }
  header h1 { font-size: 1.5rem; }
  .card { padding: var(--spacing-md); border-radius: var(--radius-sm); }
  .radio-option label { padding: 0.5rem 0.75rem; font-size: 0.8125rem; }
  .bac-value { font-size: 2rem; }
}

@media (min-width: 481px) and (max-width: 768px) {
  #app { padding: var(--spacing-md); }
}

footer {
  text-align: center;
  padding: var(--spacing-xl) var(--spacing-md) var(--spacing-md);
  color: var(--text-hint);
  font-size: 0.75rem;
}

footer p { color: var(--text-hint); font-size: 0.75rem; }