style.css

@import url("https://fonts.googleapis.com/css2?family=Itim&display=swap");
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  font-family: "Itim", cursive;
}
button {
  appearance: none;
  outline: none;
  border: none;
  background: none;
  cursor: pointer;
}
body {
  background-color: #242928;
  color: #fff;
}
main {
  min-height: 100vh;
  display: flex;
  justify-content: center;
  padding: 2rem 1.5rem;
}
.app {
  width: 100%;
  max-width: 768px;
}
.app header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 1rem;
}
.app header h1 {
  color: #fff;
  font-size: 24px;
  font-weight: 400;
}
.app header button {
  color: #fff;
  font-size: 24px;
}
.item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1.5rem;
  border-radius: 1rem;
  background-color: #1e1e1e;
  box-shadow: 0 0 0 4px rgba(0, 0, 0, 0.1);
  margin-bottom: 1.5rem;
}
.item:last-of-type {
  margin-bottom: 0;
}
.item input[type="checkbox"] {
  margin-right: 1rem;
}
.item input[type="text"] {
  appearance: none;
  border: none;
  outline: none;
  background: none;
  font-family: 400;
  color: #fff;
  font-size: 20px;
  flex: 1 1 0%;
  margin-right: 1rem;
}
.item input[type="text"]:not:disabled {
  border-bottom: 2px solid #fff;
}
.item.complete {
  opacity: 0.7;
}
.item.item.complete input[type="text"] {
  text-decoration: line-through;
}
.item:hover,
.item:focus-within {
  outline: 2px solid #fff;
}
.actions button {
  color: #fff;
  margin-right: 1rem;
  opacity: 0.8;
  transform: 0.1s;
}
.actions button.remove-btn {
  color: crimson;
}
.actions button:hover {
  opacity: 1;
}
.actions button:last-of-type {
  margin-right: 0;
}