:root {
  --color-bg: #f5f6fa;
  --color-surface: #ffffff;
  --color-primary: #4a63e7;
  --color-primary-dark: #3949c4;
  --color-text: #1f2430;
  --color-text-muted: #6b7280;
  --color-border: #e2e4ea;
  --color-danger: #e5484d;
  --color-danger-bg: #fdecec;
  --radius: 10px;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: var(--color-bg);
  color: var(--color-text);
  display: flex;
  justify-content: center;
  padding: 2.5rem 1rem;
}

.app {
  width: 100%;
  max-width: 640px;
}

.top-nav {
  display: flex;
  gap: 0.5rem;
  background: var(--color-surface);
  border-radius: var(--radius);
  padding: 0.4rem;
  margin-bottom: 1.5rem;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.06);
}

.nav-link {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 0.55rem 0.75rem;
  border-radius: 8px;
  text-decoration: none;
  font-weight: 600;
  font-size: 0.9rem;
  color: var(--color-text-muted);
}

.nav-link:hover {
  background: var(--color-bg);
  color: var(--color-text);
}

.nav-link.active {
  background: var(--color-primary);
  color: #fff;
}

.app-header {
  text-align: center;
  margin-bottom: 1.5rem;
}

.app-header h1 {
  font-size: 1.6rem;
  margin: 0 0 0.5rem;
}

.subtitle {
  color: var(--color-text-muted);
  margin: 0;
  font-size: 0.95rem;
}

.app-footer {
  margin-top: 1.5rem;
  text-align: center;
  color: var(--color-text-muted);
  font-size: 0.5rem;
}

main {
  background: var(--color-surface);
  border-radius: var(--radius);
  padding: 1.5rem;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.06);
}

.subjects-table {
  width: 100%;
  border-collapse: collapse;
}

.subjects-table th {
  text-align: left;
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.03em;
  color: var(--color-text-muted);
  padding: 0 0.4rem 0.5rem;
  font-weight: 600;
}

.subjects-table td {
  padding: 0.35rem;
  vertical-align: middle;
}

.col-credits, .col-grade {
  width: 90px;
}

.col-remove {
  width: 36px;
}

.subjects-table input[type="text"],
.subjects-table input[type="number"] {
  width: 100%;
  padding: 0.5rem 0.6rem;
  border: 1px solid var(--color-border);
  border-radius: 8px;
  font-size: 0.95rem;
  background: var(--color-bg);
  color: var(--color-text);
}

.subjects-table input:focus {
  outline: none;
  border-color: var(--color-primary);
  background: var(--color-surface);
}

/* Oculta las flechas nativas de los campos numéricos: no aportan en móvil
   y liberan espacio horizontal en columnas ya angostas. */
input[type="number"] {
  appearance: textfield;
  -moz-appearance: textfield;
}

input[type="number"]::-webkit-outer-spin-button,
input[type="number"]::-webkit-inner-spin-button {
  -webkit-appearance: none;
  margin: 0;
}

.remove-row {
  width: 36px;
  height: 36px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  background: none;
  border: none;
  color: var(--color-text-muted);
  font-size: 1.1rem;
  line-height: 1;
  cursor: pointer;
  padding: 0;
  border-radius: 6px;
}

.remove-row:hover {
  background: var(--color-danger-bg);
  color: var(--color-danger);
}

.btn {
  cursor: pointer;
  font-size: 0.95rem;
  border-radius: 8px;
  border: none;
  padding: 0.6rem 1rem;
}

.btn-secondary {
  margin-top: 0.5rem;
  width: 100%;
  background: var(--color-bg);
  color: var(--color-primary);
  border: 1px dashed var(--color-border);
  font-weight: 600;
}

.btn-secondary:hover {
  background: #edf0ff;
  border-color: var(--color-primary);
}

.slide-clear {
  margin-top: 0.5rem;
}

.slide-clear-track {
  position: relative;
  height: 44px;
  border-radius: 22px;
  background: var(--color-danger-bg);
  border: 1px solid var(--color-danger);
  overflow: hidden;
}

.slide-clear-label {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-danger);
  font-weight: 600;
  font-size: 0.85rem;
  pointer-events: none;
  user-select: none;
}

.slide-clear-thumb {
  position: absolute;
  top: 2px;
  left: 2px;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  border: none;
  background: var(--color-danger);
  color: #fff;
  font-size: 1rem;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: grab;
  touch-action: none;
}

.slide-clear-thumb:active {
  cursor: grabbing;
}

.target-toggle {
  margin-top: 0.75rem;
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: var(--color-bg);
  color: var(--color-primary-dark);
  border: 1px dashed var(--color-border);
  border-radius: 8px;
  font-weight: 600;
  font-size: 0.95rem;
  padding: 0.6rem 1rem;
  cursor: pointer;
}

.target-toggle:hover {
  background: #edf0ff;
  border-color: var(--color-primary);
}

.target-toggle .chevron {
  transition: transform 0.15s ease;
}

.target-toggle[aria-expanded="true"] .chevron {
  transform: rotate(180deg);
}

.target-section {
  margin-top: 1rem;
}

.target-help {
  margin: 0 0 1rem;
  padding-left: 1.25rem;
  color: var(--color-text-muted);
  font-size: 0.85rem;
  line-height: 1.5;
}

.target-help li + li {
  margin-top: 0.35rem;
}

.target-group {
  margin-top: 0;
  padding: 1rem 1.25rem;
  background: var(--color-bg);
  border-radius: var(--radius);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.target-group label {
  font-weight: 600;
  color: var(--color-text-muted);
}

.target-group input {
  width: 100px;
  padding: 0.5rem 0.6rem;
  border: 1px solid var(--color-border);
  border-radius: 8px;
  font-size: 0.95rem;
  background: var(--color-surface);
  color: var(--color-text);
  text-align: right;
}

.target-group input:focus {
  outline: none;
  border-color: var(--color-primary);
}

.result {
  margin-top: 1.5rem;
  padding: 1rem 1.25rem;
  background: var(--color-bg);
  border-radius: var(--radius);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.result-label {
  font-weight: 600;
  color: var(--color-text-muted);
}

.result-value {
  font-size: 1.6rem;
  font-weight: 700;
  color: var(--color-primary-dark);
}

.error-message {
  margin: 0.75rem 0 0;
  color: var(--color-danger);
  font-size: 0.9rem;
  text-align: center;
}

.percentage-summary {
  margin: 0.75rem 0 0;
  color: var(--color-text-muted);
  font-size: 0.85rem;
  text-align: center;
}

.percentage-summary.percentage-warning {
  color: var(--color-danger);
}

@media (max-width: 420px) {
  body {
    padding: 1.5rem 0.75rem;
  }

  main {
    padding: 1.25rem 0.75rem;
  }

  .col-credits, .col-grade {
    width: 64px;
  }

  .subjects-table td {
    padding: 0.3rem 0.2rem;
  }

  .subjects-table input[type="text"],
  .subjects-table input[type="number"] {
    padding: 0.45rem 0.4rem;
    font-size: 0.9rem;
  }
}