style.css

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}
body {
  background-image: linear-gradient(
    to right,
    #d16ba5,
    #c777b9,
    #ba83ca,
    #aa8fd8,
    #9a9ae1,
    #8aa7ec,
    #79b3f4,
    #69bff8,
    #52cffe,
    #41dfff,
    #46eefa,
    #5ffbf1
  );
  font-family: "Roboto", sans-serif;
}

#container {
  display: flex;
  flex-direction: column;
  text-align: center;
  margin: 80px auto;
  padding: 20px;
  justify-content: center;
  align-items: center;
  width: 750px;
  min-height: 800px;
  background-color: whitesmoke;
  border-radius: 15px;
  box-shadow: rgba(0, 0, 0, 0.3) 0px 19px 38px,
    rgba(0, 0, 0, 0.22) 0px 15px 12px;
}
input[type="text"],
select {
  width: 350px;
  padding: 12px 20px;
  margin: 8px 0;
  border: none;
  border-radius: 4px;
  box-shadow: rgba(0, 0, 0, 0.15) 1.95px 1.95px 2.6px;
}
input[type="button"],
select {
  width: 350px;
  padding: 12px 20px;
  margin: 8px 0;
  border: none;
  border-radius: 4px;
  box-shadow: rgba(0, 0, 0, 0.15) 1.95px 1.95px 2.6px;
}

#adding_todo {
  display: flex;
  flex-direction: column;
}

h2 {
  font-size: 40px;
  padding-bottom: 10px;
}

li {
  margin-top: 20px;
  display: flex;
  flex-direction: column;
  font-size: 20px;
  text-decoration: none;
  cursor: pointer;
}

li:hover {
  color: #ff4000;
  text-decoration: line-through;
}

footer {
  color: white;
  bottom: 0;
  width: 100%;
  padding: 15px 0px;
  text-align: center;
}

a {
  color: white;
  text-decoration: underline;
}

a:visited {
  color: white;
  text-decoration: underline;
}