:root {
  --bg: #f7f7f8;
  --card-bg: #ffffff;
  --text: #1b1b1f;
  --muted: #6b7280;
  --accent: #2563eb;
  --accent-hover: #1d4ed8;
  --border: #e5e7eb;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Apple SD Gothic Neo",
    "Malgun Gothic", Roboto, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  display: flex;
  justify-content: center;
  padding: 40px 16px;
}

.page {
  width: 100%;
  max-width: 480px;
}

h1 {
  font-size: 1.6rem;
  margin-bottom: 4px;
}

.subtitle {
  color: var(--muted);
  margin-top: 0;
  margin-bottom: 28px;
  font-size: 0.95rem;
}

.back-link {
  display: inline-block;
  margin-bottom: 20px;
  color: var(--accent);
  text-decoration: none;
  font-size: 0.9rem;
}

.back-link:hover {
  text-decoration: underline;
}

.tool-list {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.tool-link {
  display: block;
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 16px 18px;
  text-decoration: none;
  color: var(--text);
  transition: border-color 0.15s ease, transform 0.05s ease;
}

.tool-link:hover {
  border-color: var(--accent);
}

.tool-link:active {
  transform: scale(0.99);
}

.tool-link .name {
  font-weight: 600;
  font-size: 1.02rem;
}

.tool-link .desc {
  color: var(--muted);
  font-size: 0.85rem;
  margin-top: 4px;
}

.card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 24px;
}

.mode-toggle {
  display: flex;
  gap: 8px;
  margin-bottom: 20px;
}

.mode-btn {
  flex: 1;
  padding: 9px 10px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: #fff;
  color: var(--muted);
  font-size: 0.85rem;
  font-weight: 600;
  cursor: pointer;
}

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

label {
  display: block;
  font-size: 0.88rem;
  font-weight: 600;
  margin-bottom: 6px;
  margin-top: 18px;
}

label:first-of-type {
  margin-top: 0;
}

input[type="number"],
input[type="text"] {
  width: 100%;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  font-size: 1rem;
  color: var(--text);
  background: #fff;
}

input:focus {
  outline: none;
  border-color: var(--accent);
}

.hint {
  color: var(--muted);
  font-size: 0.78rem;
  margin-top: 4px;
}

button {
  width: 100%;
  margin-top: 22px;
  padding: 12px;
  border: none;
  border-radius: 8px;
  background: var(--accent);
  color: #fff;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
}

button:hover {
  background: var(--accent-hover);
}

.result {
  margin-top: 20px;
  padding: 16px;
  border-radius: 10px;
  background: #eff6ff;
  border: 1px solid #bfdbfe;
  display: none;
}

.result.visible {
  display: block;
}

.result .label {
  font-size: 0.85rem;
  color: var(--muted);
}

.result .value {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--accent);
  margin-top: 2px;
}

.result .breakdown {
  margin-top: 10px;
  font-size: 0.85rem;
  color: var(--muted);
  line-height: 1.5;
}

.error {
  margin-top: 20px;
  padding: 12px 16px;
  border-radius: 10px;
  background: #fef2f2;
  border: 1px solid #fecaca;
  color: #b91c1c;
  font-size: 0.88rem;
  display: none;
}

.error.visible {
  display: block;
}