html, body{
  margin:0; padding:0; height:100%;
  background: url('background.jpg') no-repeat center center fixed;
  background-size: cover;
  display:flex; flex-direction:column;
}
.wrapper{ display:flex; flex-direction:column; min-height:100vh; }
.container{
  flex:1;
  background: rgba(255,255,255,.20);
  border-radius: 15px;
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border: 1px solid rgba(255,255,255,.30);
  padding: 20px;
  box-shadow: 0 6px 24px rgba(0,0,0,.25);
  margin: 20px auto 84px;
  width: min(100% - 32px, 980px);
}
.cabecera{ display:flex; align-items:center; justify-content:center; gap:14px; margin:2px 0 18px; }
.cabecera img{ width:80px; height:auto; }
.cabecera h1{ font-size: clamp(1.4rem, 3.2vw, 2.1rem); margin:0; }
.login-page .container{ background:none; border:none; box-shadow:none; backdrop-filter:none; -webkit-backdrop-filter:none; }
.col-md-4.custom-width{ max-width:500px; width:100%; background:rgba(255,255,255,.20); border-radius:15px; backdrop-filter:blur(10px); -webkit-backdrop-filter:blur(10px); border:1px solid rgba(255,255,255,.3); padding:20px; box-shadow:0 4px 8px rgba(0,0,0,.2); margin:20px auto; }
.footer{
  background: rgba(52,58,64,.70);
  width:100%; text-align:center; color:#f8f9fa;
  padding:10px 0; font-size:16px; height:auto;
  position:relative; margin-top:auto;
}
.footer a{ color:#f8f9fa; text-decoration:none; }
#backToTop{
  display:none; position:fixed; bottom:40px; right:30px; z-index:99;
  border:none; outline:none; background:#007bff; color:#fff; cursor:pointer;
  padding:10px 15px; border-radius:8px; font-size:16px; box-shadow:0 4px 6px rgba(0,0,0,.2);
}
#backToTop:hover{ background:#0056b3; }
.btn-fixed-width{ min-width:150px; text-align:center; }
@media (max-width: 576px){
  .cabecera{ flex-direction:column; gap:10px; }
  .container{ width: calc(100% - 20px); padding:16px; }
}