:root {
  --navy:        #1D273D;
  --navy-light:  #263450;
  --navy-darker: #0E1221;
  --teal:        #61A9C8;
  --teal-dark:   #265B72;
  --blue-gray:   #7188BB;
  --light-blue:  #B8C3DD;
  --pale-blue:   #C6CFE4;
  --off-white:   #EDF0F2;
  --warn:        #E57373;
  --gold:        #F2D58F;

  --rule-soft: rgba(97, 169, 200, 0.12);
  --rule-med:  rgba(97, 169, 200, 0.30);
  --rule-strong: rgba(97, 169, 200, 0.55);

  --highlight: rgba(97, 169, 200, 0.10);
  --highlight-strong: rgba(97, 169, 200, 0.18);

  --font-display: 'Cormorant Garamond', Georgia, 'Times New Roman', serif;
  --font-body:    'Nunito Sans', Helvetica, Arial, sans-serif;

  --max-width: 940px;
  --gutter: 3rem;
}

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

html { background: var(--navy); }

body {
  background: var(--navy);
  color: var(--off-white);
  font-family: var(--font-body);
  font-size: 16px;
  font-weight: 400;
  line-height: 1.55;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body::before {
  content: '';
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 0;
  background:
    radial-gradient(ellipse at 10% 0%, rgba(97, 169, 200, 0.08), transparent 50%),
    radial-gradient(ellipse at 95% 100%, rgba(113, 136, 187, 0.06), transparent 55%);
}

@keyframes fadeUp {
  from { opacity: 0; transform: translateY(10px); }
  to   { opacity: 1; transform: translateY(0); }
}

/* ── Header ────────────────────────────────────── */

header {
  padding: 3rem var(--gutter) 2.5rem;
  text-align: center;
  border-bottom: 1px solid var(--rule-soft);
  position: relative;
  z-index: 1;
  animation: fadeUp 0.5s ease both;
}

.brand-kicker {
  font-family: var(--font-body);
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.24em;
  text-transform: uppercase;
  color: var(--teal);
  margin-bottom: 0.65rem;
}

.brand-title {
  font-family: var(--font-display);
  font-weight: 600;
  font-size: clamp(2.4rem, 5.5vw, 3.8rem);
  line-height: 1.05;
  color: var(--teal);
  letter-spacing: -0.01em;
  margin: 0;
}

.brand-desc {
  margin: 1rem auto 0;
  max-width: 640px;
  font-family: var(--font-display);
  font-style: italic;
  font-weight: 400;
  font-size: 1.15rem;
  line-height: 1.55;
  color: var(--light-blue);
}

.brand-desc em {
  font-style: italic;
  color: var(--teal);
  font-weight: 500;
}

.meta-marca {
  font-family: var(--font-body);
  font-size: 0.7rem;
  font-weight: 400;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--light-blue);
}

/* ── Main ──────────────────────────────────────── */

main {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 3rem var(--gutter) 4rem;
  position: relative;
  z-index: 1;
}

.cabecera {
  margin-bottom: 2.5rem;
  text-align: center;
  animation: fadeUp 0.5s ease both;
}

.cabecera::before {
  content: 'Problema';
  display: block;
  font-family: var(--font-body);
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--teal);
  margin-bottom: 0.75rem;
}

.titulo {
  display: block;
  width: 100%;
  border: none;
  background: transparent;
  font-family: var(--font-display);
  font-weight: 600;
  font-size: clamp(2.2rem, 5vw, 3.6rem);
  line-height: 1.05;
  color: var(--teal);
  padding: 0;
  letter-spacing: -0.005em;
  text-align: center;
}

.titulo::placeholder {
  color: var(--teal-dark);
  font-style: italic;
  font-weight: 400;
}

.titulo:focus { outline: none; }

/* ── Panel base ────────────────────────────────── */

.panel,
.formulacion,
.datos,
.grafico-panel,
.bloque-manual,
.bloque-optimo {
  background: var(--navy-light);
  border: 1px solid var(--rule-soft);
  border-radius: 14px;
  padding: 1.75rem 2rem;
  transition: border-color 0.3s;
}

.panel:hover,
.bloque-manual:hover,
.bloque-optimo:hover { border-color: var(--rule-med); }

/* ── Formulación matemática ────────────────────── */

.formulacion {
  margin-bottom: 1.25rem;
  padding: 2rem 2.25rem;
  animation: fadeUp 0.5s ease 0.05s both;
}

.formula {
  font-family: var(--font-display);
  font-size: 1.4rem;
  line-height: 2.2;
  color: var(--off-white);
}

.formula-fila {
  display: flex;
  align-items: baseline;
  gap: 1.5rem;
  flex-wrap: wrap;
}

.formula-kw {
  font-family: var(--font-body);
  font-size: 0.68rem;
  font-weight: 600;
  letter-spacing: 0.24em;
  text-transform: uppercase;
  color: var(--teal);
  flex-shrink: 0;
  min-width: 6.5rem;
}

.formula-expr {
  display: inline-flex;
  align-items: baseline;
  gap: 0.4rem;
  flex-wrap: wrap;
}

.formula .sigma {
  font-family: var(--font-display);
  font-size: 1.8em;
  line-height: 0.7;
  color: var(--teal);
  font-style: normal;
  margin-right: -0.05rem;
  font-weight: 400;
}

.formula .sub-i {
  font-family: var(--font-display);
  font-style: italic;
  font-weight: 400;
  font-size: 0.65em;
  color: var(--light-blue);
  align-self: flex-end;
  margin-bottom: 0.2em;
  margin-right: 0.35rem;
}

.formula .dot {
  color: var(--light-blue);
  margin: 0 0.05rem;
  font-size: 0.85em;
}

.formula .var {
  font-family: var(--font-display);
  font-style: italic;
  font-weight: 400;
  font-size: 1.1em;
  color: var(--off-white);
}

.formula .var sub {
  font-size: 0.55em;
  font-style: italic;
  font-family: var(--font-display);
}

.formula .op {
  font-family: var(--font-display);
  font-size: 1.15em;
  margin: 0 0.35rem;
  color: var(--teal);
  font-weight: 600;
}

.formula .set {
  font-family: var(--font-display);
  font-style: italic;
  font-size: 1.05em;
  color: var(--light-blue);
}

.formula .paren-meta {
  color: var(--light-blue);
  font-size: 0.85em;
  margin-left: 0.4rem;
  font-family: var(--font-body);
}

.lbl {
  font-family: var(--font-display);
  font-style: italic;
  font-size: 1em;
  font-weight: 600;
  background: transparent;
  border: none;
  border-bottom: 1px dashed var(--rule-med);
  padding: 0 0.25rem 0.15rem;
  field-sizing: content;
  min-width: 4ch;
  color: inherit;
  text-align: center;
  transition: border-color 0.2s ease;
}

.lbl:hover {
  border-bottom-color: var(--teal);
  border-bottom-style: solid;
}

.lbl:focus {
  outline: none;
  border-bottom-color: var(--teal);
  border-bottom-style: solid;
}

.lbl-valor  { color: var(--teal); }
.lbl-coste  { color: var(--light-blue); }
.lbl-limite {
  color: var(--light-blue);
  font-size: 0.88em;
}

.formula .limite {
  font-family: var(--font-body);
  font-size: 1rem;
  font-weight: 600;
  width: 5.5rem;
  text-align: right;
  background: transparent;
  border: none;
  border-bottom: 1px solid var(--teal);
  padding: 0.1rem 0.5rem;
  color: var(--off-white);
  font-variant-numeric: tabular-nums;
  -moz-appearance: textfield;
}

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

.formula .limite:focus {
  outline: none;
  border-bottom-color: var(--gold);
}

/* ── Acciones ──────────────────────────────────── */

.acciones {
  display: flex;
  gap: 0.65rem;
  margin-top: 1.75rem;
  flex-wrap: wrap;
}

button {
  font-family: var(--font-body);
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  padding: 0.7rem 1.4rem;
  border: 1px solid var(--rule-med);
  background: transparent;
  color: var(--off-white);
  cursor: pointer;
  border-radius: 999px;
  transition: all 0.25s ease;
}

button:hover:not(:disabled) {
  background: rgba(97, 169, 200, 0.1);
  border-color: var(--teal);
  color: var(--off-white);
}

button:disabled { opacity: 0.35; cursor: not-allowed; }

.btn-primario {
  background: var(--teal);
  color: var(--navy);
  border-color: var(--teal);
}

.btn-primario:hover:not(:disabled) {
  background: var(--off-white);
  color: var(--navy);
  border-color: var(--off-white);
}

#error {
  margin-top: 1rem;
  color: var(--warn);
  font-style: italic;
  min-height: 1.2em;
  font-size: 0.9rem;
}

/* ── Tabla ─────────────────────────────────────── */

.datos {
  margin-bottom: 1.25rem;
  padding: 1.5rem 1.5rem 1.25rem;
  animation: fadeUp 0.5s ease 0.1s both;
}

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

thead th {
  font-family: var(--font-body);
  font-size: 0.68rem;
  font-weight: 600;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--teal);
  text-align: left;
  padding: 0.75rem 0.6rem;
  border-bottom: 1px solid var(--rule-med);
}

thead th.num { text-align: right; }
thead th.col-check, thead th.col-id, thead th.col-opt, thead th.col-del {
  width: 1px;
  white-space: nowrap;
  text-align: center;
}

thead th.col-opt {
  color: var(--gold);
  font-size: 0.85rem;
  letter-spacing: 0;
}

tbody td {
  padding: 0.65rem 0.6rem;
  border-bottom: 1px solid var(--rule-soft);
  font-size: 1rem;
  vertical-align: middle;
  color: var(--off-white);
}

tbody td.col-id {
  font-family: var(--font-body);
  color: var(--light-blue);
  text-align: center;
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.05em;
  width: 1px;
  white-space: nowrap;
}

tbody td.col-check, tbody td.col-opt, tbody td.col-del {
  text-align: center;
  width: 1px;
}

tbody td.col-opt {
  font-family: var(--font-display);
  color: var(--gold);
  font-size: 1.3rem;
  line-height: 1;
  font-weight: 600;
}

tbody tr.en-optimo { background: var(--highlight); }

tbody tr.en-optimo td { border-bottom-color: var(--rule-med); }

tbody tr.en-optimo td:first-child {
  box-shadow: inset 3px 0 0 var(--gold);
}

tbody td input {
  width: 100%;
  border: none;
  background: transparent;
  padding: 0.3rem 0.4rem;
  font-family: var(--font-body);
  font-size: 0.98rem;
  color: var(--off-white);
  border-radius: 6px;
  transition: background 0.15s ease;
}

tbody td input:hover { background: rgba(97, 169, 200, 0.08); }

tbody td input:focus {
  outline: none;
  background: var(--navy-darker);
  box-shadow: inset 0 -1px 0 var(--teal);
}

tbody td input[type=number] {
  text-align: right;
  font-variant-numeric: tabular-nums;
  font-weight: 600;
  color: var(--light-blue);
  -moz-appearance: textfield;
}

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

input[type=checkbox] {
  accent-color: var(--teal);
  cursor: pointer;
  width: 14px;
  height: 14px;
}

.btn-borrar {
  width: 24px;
  height: 24px;
  padding: 0;
  border: none;
  background: transparent;
  color: var(--light-blue);
  font-size: 1.2rem;
  line-height: 1;
  font-family: var(--font-body);
  font-weight: 300;
  letter-spacing: 0;
  cursor: pointer;
  border-radius: 50%;
  transition: all 0.2s ease;
}

.btn-borrar:hover {
  color: var(--warn);
  background: rgba(229, 115, 115, 0.1);
}

.pie-tabla {
  margin-top: 0.75rem;
  padding-top: 0.75rem;
  border-top: 1px solid var(--rule-soft);
}

.btn-anadir {
  background: transparent;
  border: 1px dashed var(--rule-med);
  color: var(--teal);
  font-family: var(--font-body);
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.18em;
  padding: 0.55rem 1.1rem;
  text-transform: uppercase;
  border-radius: 999px;
}

.btn-anadir:hover {
  color: var(--navy);
  background: var(--teal);
  border-color: var(--teal);
  border-style: solid;
}

/* ── Resumen ───────────────────────────────────── */

.resumen {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.25rem;
  margin-bottom: 1.25rem;
  animation: fadeUp 0.5s ease 0.15s both;
}

.bloque-manual,
.bloque-optimo {
  padding: 1.75rem 2rem;
}

.bloque-optimo {
  background: linear-gradient(180deg, var(--navy-light) 0%, rgba(38, 91, 114, 0.4) 100%);
  border-color: var(--rule-med);
}

.resumen h3 {
  font-family: var(--font-body);
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--teal);
  margin: 0 0 1.25rem;
}

.bloque-optimo h3 { color: var(--gold); }

.resumen dl {
  margin: 0;
  display: grid;
  grid-template-columns: 1fr auto;
  column-gap: 1.5rem;
  row-gap: 0.6rem;
  align-items: baseline;
}

.resumen dt {
  font-family: var(--font-display);
  font-style: italic;
  font-weight: 400;
  color: var(--light-blue);
  font-size: 1.05rem;
}

.resumen dd {
  margin: 0;
  font-family: var(--font-body);
  font-weight: 600;
  font-variant-numeric: tabular-nums;
  font-size: 1rem;
  color: var(--off-white);
  text-align: right;
}

.resumen dd.big {
  font-family: var(--font-display);
  font-style: italic;
  font-weight: 600;
  font-size: 1.5rem;
  line-height: 1;
  color: var(--teal);
  text-align: right;
  letter-spacing: -0.01em;
  font-variant-numeric: normal;
}

#manual-coste.alerta {
  color: var(--warn);
  font-weight: 700;
}

#gap-valor.positivo { color: var(--warn); }
#gap-valor.cero {
  color: var(--gold);
  font-weight: 700;
}

.oculto { display: none !important; }

/* ── Gráfico ───────────────────────────────────── */

.grafico-panel {
  padding: 1.75rem 2rem 1.5rem;
  margin-bottom: 1.25rem;
  animation: fadeUp 0.5s ease both;
}

.grafico-cabecera {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  margin-bottom: 1.25rem;
  flex-wrap: wrap;
  gap: 0.5rem;
  padding-bottom: 0.85rem;
  border-bottom: 1px solid var(--rule-soft);
}

.grafico-panel h3 {
  font-family: var(--font-display);
  font-weight: 600;
  font-size: 1.6rem;
  color: var(--teal);
  margin: 0;
  letter-spacing: -0.01em;
  line-height: 1.1;
}

.grafico-meta {
  font-family: var(--font-body);
  font-size: 0.68rem;
  font-weight: 600;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--light-blue);
}

.grafico-wrapper {
  position: relative;
  height: 380px;
  width: 100%;
}

/* ── Footer ────────────────────────────────────── */

footer {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 3rem var(--gutter) 4rem;
  border-top: 1px solid var(--rule-soft);
  position: relative;
  z-index: 1;
}

.footer-kicker {
  font-family: var(--font-body);
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--teal);
  margin-bottom: 1.5rem;
}

.footer-links {
  list-style: none;
  padding: 0;
  margin: 0;
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0.65rem 1rem;
}

.footer-links li { margin: 0; }

.footer-links a {
  display: block;
  padding: 1rem 1.25rem;
  background: var(--navy-light);
  border: 1px solid var(--rule-soft);
  border-radius: 12px;
  text-decoration: none;
  color: inherit;
  transition: all 0.25s ease;
}

.footer-links a:hover {
  border-color: var(--teal);
  transform: translateY(-2px);
}

.footer-links .link-title {
  display: block;
  font-family: var(--font-display);
  font-weight: 500;
  font-size: 1.05rem;
  color: var(--off-white);
  line-height: 1.3;
  margin-bottom: 0.35rem;
}

.footer-links a:hover .link-title { color: var(--teal); }

.footer-links .link-host {
  display: block;
  font-family: var(--font-body);
  font-size: 0.68rem;
  font-weight: 600;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--light-blue);
}

@media (max-width: 720px) {
  .footer-links { grid-template-columns: 1fr; }
}

/* ── Responsive ────────────────────────────────── */

@media (max-width: 720px) {
  :root { --gutter: 1.25rem; }
  .titulo { font-size: 2.2rem; }
  .formula { font-size: 1.15rem; line-height: 2; }
  .formula-fila { gap: 1rem; }
  .formula-kw { min-width: 0; font-size: 0.62rem; }
  .formulacion { padding: 1.5rem 1.25rem; }
  .resumen {
    grid-template-columns: 1fr;
    gap: 1rem;
  }
  .bloque-manual, .bloque-optimo { padding: 1.25rem 1.5rem; }
  .resumen dd.big { font-size: 2.4rem; }
  .grafico-panel { padding: 1.25rem 1.25rem 1rem; }
}