header {
  position: sticky;
  top: 0;
  z-index: 1000;
  background: linear-gradient(90deg, #061b2f, #004e92);
  color: white;
  height: 64px;
  padding: 0 32px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
nav a {
  margin-left: 25px;
  text-decoration: none;
  color: rgba(255,255,255,0.9);
  font-weight: bold;
  letter-spacing: 0.5px;
}

nav a:hover {
  color: #f30a0a;
}
.logo {
  font-size: 36px;
  font-weight: bold;
  color: #eef0f3;
}

body{
    font-family: Arial, Helvetica, sans-serif;
    margin:0;
    background:#f5f7fa;
    color:#222;
    line-height:1.6;
}

.articulo p{
    text-align: justify;
}

.container{
    max-width:1000px;
    margin:auto;
    background:white;
    padding:40px;
}

h1{
    font-size:34px;
    margin-bottom:20px;
    color:#0a3d62;
}

h2{
    margin-top:40px;
    color:#1e5f9e;
}

h3{
    margin-top:25px;
}

p{
    margin:15px 0;
}

.formula{
    background:#f3f6fa;
    padding:15px;
    border-left:4px solid #2c6db2;
    margin:20px 0;
    font-size:20px;
    text-align:center;
}

table{
    width:100%;
    border-collapse:collapse;
    margin:25px 0;
}

th,td{
    border:1px solid #ddd;
    padding:10px;
    text-align:center;
}

th{
    background:#1e5f9e;
    color:white;
}

.note{
    background:#fff8e1;
    padding:15px;
    border-left:4px solid #ffc107;
    margin:20px 0;
}

.related{
    margin-top:50px;
    padding-top:20px;
    border-top:2px solid #eee;
}

.related a{
    display:block;
    margin:8px 0;
    color:#1e5f9e;
    text-decoration:none;
}

.related a:hover{
    text-decoration:underline;
}

footer{
    margin-top:60px;
    padding-top:20px;
    border-top:1px solid #ddd;
    font-size:14px;
    color:#777;
}

.btnGuia {
    padding: 5px 12px;
    border: 1px solid #999;
    border-radius: 5px;
    background: #f5f5f5;
    cursor: pointer;
    font-size: 13px;
    transition: all 0.15s;
}

.btnGuia:hover {
    background: #e6e6e6;
}

.btnGuia:active {
    background: #dcdcdc;
    transform: scale(0.97);
}

.select {
    padding: 4px 6px;
    border: 1px solid #999;
    border-radius: 4px;
    font-size: 13px;
    width: 70px;
    text-align: right;
}

.select:focus {
    outline: none;
    border-color: #0078d7;
}

#slider {
    width: 140px;
    height: 4px;
    background: #ccc;
    border-radius: 3px;
    outline: none;
    cursor: pointer;
}

/* bolita */
#slider::-webkit-slider-thumb {
    appearance: none;
    width: 12px;
    height: 12px;
    background: #d70048;
    border-radius: 50%;
    cursor: pointer;
}

#slider::-moz-range-thumb {
    width: 12px;
    height: 12px;
    background: #0400d7;
    border-radius: 50%;
    cursor: pointer;
}

footer {
  background: #003f73;
  color: white;
  padding: 40px;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 20px;
}

footer h4 {
  margin-top: 0;
  color: #7ec8ff;
}

footer a {
  display: block;
  color: #d9efff;
  text-decoration: none;
  margin: 6px 0;
}

footer a:hover {
  text-decoration: underline;
}