* {
  box-sizing: border-box;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

body {
  margin: 0;
  background: #0f172a;
  color: #e5e7eb;
}

header {
  text-align: center;
  padding: 2rem 1rem;
  background: #020617;
  border-bottom: 1px solid #1f2937;
}

nav {
  display: flex;
  justify-content: center;
  gap: 0.5rem;
  padding: 1rem;
  background: #020617;
}

.tab-btn {
  border: none;
  padding: 0.6rem 1rem;
  border-radius: 999px;
  background: #1f2937;
  color: #e5e7eb;
  cursor: pointer;
}

.tab-btn.active {
  background: #2563eb;
}

main {
  max-width: 900px;
  margin: 0 auto;
  padding: 1.5rem;
}

.tool-section {
  display: none;
}

.tool-section.active {
  display: block;
}

.tool-card {
  background: #020617;
  border-radius: 0.75rem;
  padding: 1.5rem;
  border: 1px solid #1f2937;
}

label {
  display: block;
  margin-bottom: 0.75rem;
}

input[type="number"],
input[type="text"],
textarea,
select {
  width: 100%;
  margin-top: 0.25rem;
  padding: 0.5rem;
  border-radius: 0.5rem;
  border: 1px solid #374151;
  background: #020617;
  color: #e5e7eb;
}

textarea {
  resize: vertical;
}

input[type="range"] {
  width: 100%;
  margin: 0.5rem 0 1rem;
  cursor: pointer;
}

.checkbox-group {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

button {
  border: none;
  padding: 0.6rem 1rem;
  border-radius: 0.5rem;
  background: #2563eb;
  color: #e5e7eb;
  cursor: pointer;
}

button:hover {
  background: #1d4ed8;
}

.output-group {
  display: flex;
  gap: 0.5rem;
  margin-top: 1rem;
}

.btn-row {
  display: flex;
  gap: 0.5rem;
  margin-top: 0.5rem;
}

footer {
  text-align: center;
  padding: 1rem;
  color: #6b7280;
  border-top: 1px solid #1f2937;
}

select {
  background: #020617;
  color: #e5e7eb;
}