body {
  font-family: serif;
  background: transparent;
  color: #e6ffe6;
  margin: 0;
  padding: 5%;
  min-height: 100%;
  display: block; /* normal flow */
}

/* Stack content vertically and center it */
h3, table, .graph-wrapper {
  margin: 1em auto; /* vertical spacing + horizontal centering */
  max-width: 800px; /* optional max width */
}

/* Let tables fit content naturally */
table {
  border-collapse: collapse;
  width: auto; /* only as wide as content */
}

table th, table td {
  padding: 8px;
  border: 1px solid #e6ffe6;
  text-align: left;
  white-space: nowrap; /* prevents cells from stretching */
}

/* iframe wrapper */
.graph-wrapper {
  width: 100%;
  max-width: 800px;
}

.graph-wrapper iframe {
  width: 100%;
  height: 400px;
  border: none;
  display: block;
}