body {
  display: flexbox;
  font-family: 'Segoe UI', Tahoma;
}
.btns {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0px
}
button {
  padding: 15px;
  text-align: center;
  background-color: #FFFFFF;
  color: black;
  border-color: #000000;
  border-radius: 5px;
  margin: 2px;
  transition: background-color 0.3s;
}
button:hover {
  background-color: #C4C2BC;
}
.zero {
  grid-column: span 2;
}
.cal {
  width: 100%;
  background-color: lightskyblue;
}
.cal:hover {
  background-color: deepskyblue;
}
input {
  border-radius: 10px;
  width: 300px;
  height: 40px;
  font-size: 24px;
}

footer {
  background-color: #42445A;
  width: 100%;
  color: white;
  text-align: center;
  height: 60px;
  align-content: center;
  font-weight: bolder;
  bottom: 0;
  left: 0;
  position: fixed;
}
.addond {
  color: #696B7D;
}

nav {
  background-color: #42445A;
}
nav ul {
  list-style-type: none;
  margin: 0;
  padding: 5px;
}
nav li {
  
}
nav li a {
  display: block;
  color: white;
  text-align: center;
  padding: 10px 12px;
  text-decoration: none;
  width: 100%;
}
nav li a:hover {
  background-color: #AFB5EE;
}