style.css

@import url("https://fonts.googleapis.com/css2?family=Poppins:wght@200;400&display=swap");

* {
  box-sizing: border-box;
}

body {
  background-color: aquamarine;
 
  color: black;
;
  opacity:0.8;
  font-family: "Poppins", sans-serif;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  margin: 0;
}
img.background {
    position: absolute;
    left: 0px;
    top: 0px;
    z-index: -1;
    width: 100%;
    height: 100%;
    -webkit-filter: blur(5px); /* Safari 6.0 - 9.0 */
    filter: blur(5px);
}
h1 {
  color:black;
  font-size: 10rem;
  text-align: center;
 padding-left: 5rem;
}
form {
  box-shadow: 0 4px 10px rgba(0, 0, 0, 0.1);
  max-width: 100%;
  width: 400px;
}
.input {
  border: none;
  color: #444;
  font-size: 2rem;
  padding: 1rem 2rem;
  display: block;
  width: 100%;
}
.input::placeholder {
  color: #d5d5d5;
}
.input:focus {
  outline-color: rgb(179, 131, 226);
}
.todos {
  background-color: #fff;
  padding: 0;
  margin: 0;
  list-style-type: none;
}
.todos li {
  border-top: 1px solid #e5e5e5;
  cursor: pointer;
  font-size: 1.5rem;
  padding: 1rem 2rem;
}
.todos li.completed {
  color: #b6b6b6;
  text-decoration: line-through;
}
small {
  color: #b5b5b5;
  margin-top: 3rem;
  text-align: center;
}