:root{
  --bg:#eaf0f9;
  --panel:#ffffff;
  --panel-border:#d0dced;
  --text:#1a2433;
  --muted:#5b6b84;
  --input-bg:#f7faff;
  --input-border:#c1d0e6;
  --btn:#f1f6fd;
  --btn-border:#bfd0e7;
  --btn-hover:#e4eefc;
  --accent:#1663d3;
  --accent-strong:#0e50b0;
  --danger:#c33434;
  --danger-hover:#a92a2a;
  --warn:#ffbe4b;
  --warn-hover:#ecad42;
  --history-bg:#f6f9fd;
}
*{box-sizing:border-box;}
body{
  margin:0;
  padding:28px 14px;
  background: url('path/to/your/sydney-opera-house-on-io-with-jupiter.jpg') no-repeat center center fixed; 
  background-size: cover; 
  color:var(--text);
  font-family:"Avenir Next","Segoe UI",Roboto,Arial,sans-serif;
}
.nav{
  display: flex;
  justify-content: space-between;
  padding: 16px 0;
  background-color: var(--panel);
}
.nav a{
  color: var(--text);
  text-decoration: none;
  font-weight: 600;
  padding: 8px 16px;
  position: relative; /* Make this element a positioning context */
  transition: background-color 0.3s ease;
  border-radius: 4px; /* Adding border radius for a smoother look */
}
.nav a:hover{
  background-color: var(--btn-hover);
}
.projects-dropdown {
  display: none; /* Initially hidden */
  position: absolute; /* Position below Projects link */
  top: 100%; /* Position just below the nav item */
  left: 0;
  background-color: var(--panel);
  border: 1px solid var(--panel-border);
  box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
  min-width: 150px;
  z-index: 1000;
  border-radius: 4px; /* Rounded corners for the dropdown */
}
.nav a:hover + .projects-dropdown,
.nav a:focus + .projects-dropdown {
  display: block; /* Show on hover or focus */
}
.projects-dropdown a {
  display: block;
  padding: 8px 16px;
  color: var(--text);
  text-decoration: none;
}
.projects-dropdown a:hover {
  background-color: var(--btn-hover);
}
.calc-shell{
  max-width:760px;
  margin:0 auto;
  background:var(--panel);
  border:1px solid var(--panel-border);
  border-radius:22px;
  box-shadow:0 20px 46px rgba(23,42,69,0.14);
  padding:20px 20px 18px;
}
h1{
  margin:0 0 16px;
  font-size:29px;
  line-height:1.1;
  letter-spacing:0.01em;
}
.calc-form{display:flex;gap:10px;align-items:stretch;}
.calc-form input{
  flex:1;
  min-width:0;
  padding:12px 14px;
  font-size:17px;
  border-radius:13px;
  border:1px solid var(--input-border);
  background:var(--input-bg);
  color:var(--text);
  font-family:"SF Mono","Menlo","Consolas",monospace;
  letter-spacing:0.01em;
}
.calc-form input:focus{
  outline:none;
  border-color:var(--accent);
  box-shadow:0 0 0 3px rgba(42,111,214,0.18);
}
.calc-form input[readonly]{cursor:default;}
.compute-btn{
  border:0;
  border-radius:12px;
  background:var(--accent);
  color:#fff;
  font-size:15px;
  font-weight:700;
  padding:0 16px;
  min-width:110px;
  cursor:pointer;
  transition:background .15s ease;
}
.compute-btn:hover{background:var(--accent-strong);}
.helper{
  margin:10px 2px 10px;
  font-size:13px;
  color:var(--muted);
}
.error{
  margin:8px 2px 12px;
  font-size:14px;
  font-weight:700;
  color:#b00020;
}
.pad{
  display:grid;
  grid-template-columns:minmax(0,0.95fr) minmax(0,1.15fr);
  gap:12px;
  margin-top:8px;
  align-items:start;
}
.pad-group{
  background:#f9fbfe;
  border:1px solid #d7e1ef;
  border-radius:14px;
  padding:10px 10px 12px;
  display:grid;
  gap:8px;
}
.pad-group-title{
  font-size:11px;
  letter-spacing:0.1em;
  font-weight:700;
  text-transform:uppercase;
  color:#6b7890;
  margin:0 0 2px;
}
.grid-4{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:8px;}
.grid-3{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:8px;}
.pad button{
  border:1px solid var(--btn-border);
  border-radius:10px;
  background:var(--btn);
  color:var(--text);
  font-size:14px;
  font-weight:600;
  padding:11px 8px;
  min-height:44px;
  cursor:pointer;
  transition:background .15s ease,border-color .15s ease,transform .04s ease;
}
.pad button:hover{background:var(--btn-hover);border-color:#afc1dd;}
.pad button:active{transform:translateY(1px);}
.pad button.op{background:#edf5ff;}
.pad button.func{background:#eef8f5;}
.pad button.eq{
  background:var(--accent);
  border-color:var(--accent);
  color:#fff;
  font-weight:700;
}
.pad button.eq:hover{background:var(--accent-strong);border-color:var(--accent-strong);}
.pad button.clear{
  background:var(--danger);
  border-color:var(--danger);
  color:#fff;
  font-weight:700;
}
.pad button.clear:hover{background:var(--danger-hover);border-color:var(--danger-hover);}
.pad button.back{
  background:var(--warn);
  border-color:var(--warn);
  color:#1f2430;
  font-weight:700;
}
.pad button.back:hover{background:var(--warn-hover);border-color:var(--warn-hover);}
.pad button.wide{grid-column:span 2;}
.pad button.tall{grid-row:span 2;}
.project-note{
  margin:0 2px 10px;
  font-size:13px;
  color:#526178;
}
.history{
  margin-top:16px;
  border:1px solid #d7e1ef;
  border-radius:14px;
  background:var(--history-bg);
  overflow:hidden;
}
.history-toggle{
  width:100%;
  border:0;
  padding:12px 14px;
  cursor:pointer;
  user-select:none;
  font-weight:700;
  color:#334155;
  background:transparent;
  display:flex;
  align-items:center;
  justify-content:space-between;
  gap:10px;
  text-align:left;
  font:inherit;
}
.history-toggle:hover{
  background:#f1f6fc;
}
.history-toggle[aria-expanded="true"]{
  border-bottom:1px solid #d7e1ef;
  background:#f1f6fc;
}
.history-arrow{
  font-size:14px;
  line-height:1;
  transition:transform .15s ease;
}
.history-toggle[aria-expanded="true"] .history-arrow{
  transform:rotate(180deg);
}
.history-wrap{
  padding:12px 14px;
}
.history-wrap[hidden]{
  display:none;
}
table{border-collapse:collapse;width:100%;}
th,td{border:1px solid #d8e2f0;padding:8px;text-align:left;font-size:13px;background:#fff;}
th{background:#f0f5fc;}
code{background:#edf3fb;padding:2px 6px;border-radius:6px;}
.pager{
  margin-top:12px;
  display:flex;
  align-items:center;
  justify-content:space-between;
  gap:8px;
  flex-wrap:wrap;
}
.pager-group{
  display:flex;
  align-items:center;
  justify-content:center;
  gap:6px;
  flex-wrap:wrap;
}
.pager-link,.pager-current,.pager-ellipsis{
  min-width:34px;
  height:34px;
  border-radius:9px;
  display:inline-flex;
  align-items:center;
  justify-content:center;
  font-size:13px;
  font-weight:600;
}
.pager-link{
  border:1px solid var(--btn-border);
  background:var(--btn);
  color:var(--text);
  text-decoration:none;
  padding:0 10px;
}
.pager-link:hover{background:var(--btn-hover);border-color:#afc1dd;}
.pager-current{
  border:1px solid var(--accent);
  background:var(--accent);
  color:#fff;
  padding:0 10px;
}
.pager-ellipsis{color:var(--muted);}
.pager-link.disabled{
  opacity:.45;
  pointer-events:none;
  cursor:default;
}
.home-shell{
  max-width:560px;
  text-align:center;
  padding:30px 24px 26px;
}
.home-text{
  margin:0 0 10px;
  color:var(--muted);
}
.home-actions{
  margin-top:18px;
  display:flex;
  justify-content:center;
}
@media (max-width:700px){
  .calc-shell{padding:16px;}
  .calc-form{flex-direction:column;}
  .compute-btn{min-height:44px;}
  .pad{grid-template-columns:1fr;}
  .pager{justify-content:center;}
}