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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  background: #f5f6f8;
  color: #1a1a1a;
  line-height: 1.5;
  min-height: 100vh;
}

.container {
  max-width: 900px;
  margin: 0 auto;
  padding: 24px 16px 40px;
}

.header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 32px;
  flex-wrap: wrap;
  gap: 16px;
}

.header h1 {
  font-size: 28px;
  font-weight: 600;
  color: #1a1a1a;
}

.main {
  display: flex;
  flex-direction: column;
  gap: 24px;
}

.card {
  background: #ffffff;
  border-radius: 12px;
  padding: 24px;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.08);
}

.calculator {
  max-width: 500px;
  margin: 0 auto;
  width: 100%;
}

.form-group {
  margin-bottom: 20px;
}

.form-group label {
  display: block;
  font-size: 14px;
  font-weight: 500;
  color: #52525b;
  margin-bottom: 8px;
}

.input {
  width: 100%;
  padding: 12px 16px;
  font-size: 16px;
  border: 1px solid #d4d4d8;
  border-radius: 8px;
  background: #ffffff;
  color: #1a1a1a;
  transition: border-color 0.2s, box-shadow 0.2s;
}

.input:focus {
  outline: none;
  border-color: #0066cc;
  box-shadow: 0 0 0 3px rgba(0, 102, 204, 0.1);
}

.input-select {
  font-size: 16px;
  padding: 12px 16px;
  border: 1px solid #d4d4d8;
  border-radius: 8px;
  background: #ffffff;
  color: #1a1a1a;
  cursor: pointer;
  width: 100%;
}

.input-select:focus {
  outline: none;
  border-color: #0066cc;
  box-shadow: 0 0 0 3px rgba(0, 102, 204, 0.1);
}

.input-with-suffix {
  position: relative;
  display: flex;
  align-items: center;
}

.input-with-suffix .input {
  padding-right: 80px;
}

.input-with-suffix .suffix {
  position: absolute;
  right: 16px;
  color: #71717a;
  font-size: 14px;
  pointer-events: none;
}

.btn {
  padding: 10px 20px;
  font-size: 14px;
  font-weight: 500;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  transition: background 0.2s, transform 0.1s;
}

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

.btn-primary {
  background: #0066cc;
  color: #ffffff;
}

.btn-primary:hover {
  background: #0052a3;
}

.btn-secondary {
  background: #f4f4f5;
  color: #1a1a1a;
  border: 1px solid #d4d4d8;
}

.btn-secondary:hover {
  background: #e4e4e7;
}

.btn-danger {
  background: #ef4444;
  color: #ffffff;
}

.btn-danger:hover {
  background: #dc2626;
}

.btn-small {
  padding: 6px 12px;
  font-size: 13px;
}

.btn-large {
  width: 100%;
  padding: 14px 24px;
  font-size: 16px;
  font-weight: 600;
  margin-top: 8px;
}

.result {
  text-align: center;
  display: none;
}

.result.show {
  display: block;
}

.result-title {
  font-size: 16px;
  color: #52525b;
  margin-bottom: 12px;
  font-weight: 500;
}

.result-value {
  font-size: 48px;
  font-weight: 700;
  color: #0066cc;
  margin-bottom: 24px;
}

.details {
  background: #f9fafb;
  border-radius: 8px;
  padding: 16px 20px;
  margin-bottom: 20px;
  text-align: left;
}

.details-title {
  font-size: 14px;
  color: #52525b;
  margin-bottom: 12px;
  font-weight: 500;
}

.detail-row {
  display: flex;
  justify-content: space-between;
  padding: 8px 0;
  border-bottom: 1px solid #e4e4e7;
  font-size: 15px;
}

.detail-row:last-child {
  border-bottom: none;
}

.detail-row span {
  color: #71717a;
}

.detail-row strong {
  color: #1a1a1a;
}

.formula {
  background: #f0fdf4;
  border: 1px solid #bbf7d0;
  border-radius: 8px;
  padding: 16px 20px;
  text-align: left;
}

.formula-title {
  font-size: 14px;
  color: #166534;
  margin-bottom: 8px;
  font-weight: 500;
}

.formula-text {
  font-family: "Courier New", Courier, monospace;
  font-size: 14px;
  color: #166534;
  line-height: 1.6;
  word-break: break-word;
}

.history {
  max-width: 700px;
  margin: 0 auto;
  width: 100%;
}

.history-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 16px;
}

.history-header h2 {
  font-size: 18px;
  font-weight: 600;
}

.table-wrapper {
  overflow-x: auto;
}

.table {
  width: 100%;
  border-collapse: collapse;
  font-size: 14px;
}

.table th,
.table td {
  padding: 12px 16px;
  text-align: left;
  border-bottom: 1px solid #e4e4e7;
}

.table th {
  font-weight: 600;
  color: #52525b;
  background: #f9fafb;
}

.table tbody tr:hover {
  background: #f9fafb;
}

.empty-message {
  text-align: center;
  color: #71717a;
  padding: 24px;
  display: none;
}

.empty-message.show {
  display: block;
}

/* Modal */
.modal-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0, 0, 0, 0.5);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  padding: 16px;
}

.modal {
  background: #ffffff;
  border-radius: 12px;
  width: 100%;
  max-width: 560px;
  max-height: 90vh;
  overflow-y: auto;
  box-shadow: 0 20px 50px rgba(0, 0, 0, 0.2);
}

.modal-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 20px 24px;
  border-bottom: 1px solid #e4e4e7;
}

.modal-header h2 {
  font-size: 20px;
  font-weight: 600;
}

.btn-close {
  background: none;
  border: none;
  font-size: 28px;
  color: #71717a;
  cursor: pointer;
  line-height: 1;
  padding: 0;
  width: 32px;
  height: 32px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 6px;
  transition: background 0.2s;
}

.btn-close:hover {
  background: #f4f4f5;
}

.modal-body {
  padding: 24px;
}

.tabs {
  display: flex;
  gap: 12px;
  margin-bottom: 20px;
  flex-wrap: wrap;
  align-items: center;
}

.tab-list {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  flex: 1;
}

.tab-btn {
  padding: 8px 16px;
  font-size: 14px;
  font-weight: 500;
  border: 1px solid #d4d4d8;
  background: #ffffff;
  color: #52525b;
  border-radius: 8px;
  cursor: pointer;
  transition: all 0.2s;
}

.tab-btn:hover {
  background: #f4f4f5;
}

.tab-btn.active {
  background: #0066cc;
  color: #ffffff;
  border-color: #0066cc;
}

.settings-form {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.form-row {
  display: flex;
  gap: 16px;
}

.form-row .form-group {
  flex: 1;
  margin-bottom: 0;
}

.form-actions {
  display: flex;
  gap: 12px;
  justify-content: flex-end;
  margin-top: 8px;
  padding-top: 16px;
  border-top: 1px solid #e4e4e7;
}

.save-message {
  text-align: center;
  color: #166534;
  background: #f0fdf4;
  padding: 10px 16px;
  border-radius: 6px;
  font-size: 14px;
  border: 1px solid #bbf7d0;
}

/* Responsive */
@media (max-width: 600px) {
  .header {
    flex-direction: column;
    align-items: flex-start;
  }

  .header h1 {
    font-size: 24px;
  }

  .result-value {
    font-size: 36px;
  }

  .form-row {
    flex-direction: column;
    gap: 0;
  }

  .tabs {
    flex-direction: column;
    align-items: stretch;
  }

  .tab-list {
    width: 100%;
  }

  .tab-btn {
    flex: 1;
    text-align: center;
  }

  .form-actions {
    flex-direction: column;
  }

  .form-actions .btn {
    width: 100%;
  }
}