* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Segoe UI", sans-serif;
  display: flex;
  height: 100vh;
}

header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 64px;
  background: #007bff;
  color: white;
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 999;
}

.layout {
  display: flex;
  flex: 1;
  margin-top: 64px;
  width: 100%;
  height: calc(100vh - 64px);
}

nav {
  width: 220px;
  background: #2c3e50;
  color: white;
  padding: 1em;
  height: 100%;
  overflow-y: auto;
  flex-shrink: 0;
}

nav a {
  color: white;
  text-decoration: none;
  display: block;
  margin: 0.75em 0;
}

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

main {
  flex: 1;
  padding: 2em;
  overflow-y: auto;
  background: #f4f6f8;
}

table {
  width: 100%;
  border-collapse: collapse;
  margin-top: 1em;
  background: white;
}

table, th, td {
  border: 1px solid #ccc;
}

th, td {
  padding: 0.75em;
  text-align: left;
}

form input, form select, form button, form label {
  display: block;
  margin: 0.5em 0;
  width: 100%;
  max-width: 500px;
  padding: 0.6em;
  font-size: 1em;
}

button {
  background-color: #007bff;
  color: white;
  border: none;
  cursor: pointer;
  padding: 0.6em 1.2em;
  font-size: 1em;
}

button:hover {
  background-color: #0056b3;
}

@media (max-width: 768px) {
  .layout {
    flex-direction: column;
  }

  nav {
    width: 100%;
    height: auto;
  }
}