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

:root {
  --bg-primary: #f8fafc;
  --bg-card: #ffffff;
  --bg-input: #f1f5f9;
  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-muted: #94a3b8;
  --accent: #0891b2;
  --accent-glow: rgba(8, 145, 178, 0.15);
  --success: #16a34a;
  --error: #dc2626;
  --border: #e2e8f0;
  --radius-sm: 6px;
  --radius-md: 10px;
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  min-height: 100vh;
  line-height: 1.4;
  -webkit-font-smoothing: antialiased;
}

.container {
  max-width: 400px;
  margin: 0 auto;
  padding: 16px;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.header {
  text-align: center;
  margin-bottom: 16px;
}

.header h1 {
  font-size: 1.25rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text-primary);
}

.calculator {
  background: var(--bg-card);
  border-radius: var(--radius-md);
  padding: 16px;
  display: flex;
  flex-direction: column;
  gap: 12px;
  flex: 1;
  border: 1px solid var(--border);
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.05);
}

.input-row {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.input-group {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.input-group label {
  font-size: 0.7rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-secondary);
}

.input-wrapper {
  display: flex;
  align-items: center;
  background: var(--bg-input);
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

.input-wrapper:focus-within {
  border-color: var(--accent);
  box-shadow: 0 0 0 2px var(--accent-glow);
}

.input-prefix,
.input-suffix {
  color: var(--text-muted);
  font-size: 0.8rem;
  font-weight: 500;
  padding: 0 8px;
  white-space: nowrap;
}

.input-prefix {
  padding-left: 10px;
}

.input-suffix {
  padding-right: 10px;
}

.input-wrapper input {
  flex: 1;
  background: transparent;
  border: none;
  outline: none;
  padding: 10px 8px;
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-primary);
  font-variant-numeric: tabular-nums;
  min-width: 0;
}

.input-wrapper input::placeholder {
  color: var(--text-muted);
  font-weight: 400;
  opacity: 0.7;
}

.input-wrapper input::-webkit-outer-spin-button,
.input-wrapper input::-webkit-inner-spin-button {
  -webkit-appearance: none;
  margin: 0;
}

.input-wrapper input[type="number"] {
  -moz-appearance: textfield;
}

.checkbox-row {
  display: flex;
  align-items: center;
  gap: 8px;
  cursor: pointer;
  padding: 8px 0;
}

.checkbox-row input[type="checkbox"] {
  width: 18px;
  height: 18px;
  accent-color: var(--accent);
  cursor: pointer;
}

.checkbox-row span {
  font-size: 0.85rem;
  color: var(--text-secondary);
}

.result-section {
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 16px;
  text-align: center;
}

.result-value {
  font-size: 2rem;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
  letter-spacing: -0.02em;
  transition: color 0.3s ease;
}

.result-value.positive {
  color: var(--success);
}

.result-value.negative {
  color: var(--error);
}

.result-value.neutral {
  color: var(--text-primary);
}

.result-breakdown {
  margin-top: 8px;
  font-size: 0.75rem;
  color: var(--text-muted);
  line-height: 1.5;
}

.btn-clear {
  background: var(--bg-input);
  border: 1px solid var(--border);
  color: var(--text-secondary);
  padding: 10px;
  border-radius: var(--radius-sm);
  font-size: 0.8rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s ease;
}

.btn-clear:hover {
  background: var(--border);
  color: var(--text-primary);
}

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

@media (min-width: 400px) {
  .calculator {
    max-width: 440px;
    align-self: center;
  }
}