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

:root {
  --primary: #2563eb;
  --primary-dark: #1d4ed8;
  --primary-light: #dbeafe;
  --accent: #10b981;
  --text: #1e293b;
  --text-light: #64748b;
  --bg: #f1f5f9;
  --card-bg: #ffffff;
  --border: #e2e8f0;
  --shadow: 0 10px 40px rgba(0, 0, 0, 0.08);
  --radius: 12px;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 24px 16px;
  line-height: 1.6;
}

.container {
  width: 100%;
  max-width: 480px;
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.card {
  background: var(--card-bg);
  border-radius: 20px;
  box-shadow: var(--shadow);
  overflow: hidden;
}

/* Header */
.header {
  background: linear-gradient(135deg, var(--primary), var(--primary-dark));
  padding: 32px 28px;
  text-align: center;
  color: #fff;
}

.logo {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 56px;
  height: 56px;
  background: rgba(255, 255, 255, 0.15);
  border-radius: 16px;
  margin-bottom: 12px;
}

.header h1 {
  font-size: 1.75rem;
  font-weight: 700;
  margin-bottom: 4px;
}

.subtitle {
  font-size: 0.95rem;
  opacity: 0.85;
}

/* Calculator */
.calculator {
  padding: 28px;
  display: flex;
  flex-direction: column;
  gap: 24px;
}

/* Input Groups */
.input-group {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.input-group label {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-light);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.input-wrapper,
.custom-tip {
  display: flex;
  align-items: center;
  border: 2px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  transition: border-color 0.2s;
}

.input-wrapper:focus-within,
.custom-tip:focus-within {
  border-color: var(--primary);
}

.input-prefix {
  padding: 12px 14px;
  background: #f8fafc;
  color: var(--text-light);
  font-weight: 600;
  font-size: 1rem;
  border-right: 2px solid var(--border);
}

.input-wrapper input,
.custom-tip input {
  flex: 1;
  border: none;
  outline: none;
  padding: 12px 14px;
  font-size: 1.1rem;
  font-weight: 500;
  color: var(--text);
  background: transparent;
}

.input-wrapper input::placeholder,
.custom-tip input::placeholder {
  color: #cbd5e1;
}

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

/* Tip Buttons */
.tip-buttons {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 10px;
}

.tip-btn {
  padding: 12px 8px;
  border: 2px solid var(--border);
  border-radius: var(--radius);
  background: var(--card-bg);
  font-size: 1rem;
  font-weight: 600;
  color: var(--text);
  cursor: pointer;
  transition: all 0.2s ease;
}

.tip-btn:hover {
  border-color: var(--primary);
  color: var(--primary);
  background: var(--primary-light);
}

.tip-btn.active {
  background: var(--primary);
  border-color: var(--primary);
  color: #fff;
}

/* People Control */
.people-control {
  display: flex;
  align-items: center;
  border: 2px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
}

.people-btn {
  width: 48px;
  height: 48px;
  border: none;
  background: #f8fafc;
  font-size: 1.3rem;
  font-weight: 600;
  color: var(--primary);
  cursor: pointer;
  transition: background 0.2s;
  display: flex;
  align-items: center;
  justify-content: center;
}

.people-btn:hover {
  background: var(--primary-light);
}

.people-control input {
  flex: 1;
  border: none;
  outline: none;
  text-align: center;
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--text);
  background: transparent;
}

/* Results */
.results {
  background: linear-gradient(135deg, #f0fdf4, #ecfdf5);
  border: 2px solid #bbf7d0;
  border-radius: var(--radius);
  padding: 20px;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.result-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.result-item {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.result-label {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--text-light);
  text-transform: uppercase;
  letter-spacing: 0.3px;
}

.result-value {
  font-size: 1.4rem;
  font-weight: 700;
  color: var(--text);
}

.result-value.total {
  color: var(--accent);
}

.per-person {
  padding-top: 16px;
  border-top: 1px dashed #bbf7d0;
}

/* Reset Button */
.reset-btn {
  width: 100%;
  padding: 14px;
  border: none;
  border-radius: var(--radius);
  background: var(--text);
  color: #fff;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
}

.reset-btn:hover {
  background: #334155;
  transform: translateY(-1px);
}

.reset-btn:active {
  transform: translateY(0);
}

/* Footer */
footer {
  text-align: center;
  color: var(--text-light);
  font-size: 0.85rem;
}

/* Responsive */
@media (max-width: 400px) {
  .header {
    padding: 24px 20px;
  }
  .calculator {
    padding: 20px;
  }
  .tip-buttons {
    grid-template-columns: repeat(2, 1fr);
  }
}