html {
  font-size: 10px;
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

body {
  background: rgba(9, 119, 192, 0.884);
  padding: 10rem;
}

main {
  background: white;
  border-radius: 5px;
  padding: 5rem 10rem;
  margin: 0 auto;
  width: 50%;
}

header {
  display: flex;
  justify-content: space-between;
  align-items: center;
}
header h1 {
  color: rgba(56, 55, 55, 0.658);
  font-size: 3rem;
}

header span {
  background: rgba(9, 119, 192, 0.884);
  padding: 1rem 2rem;
  border-radius: 50%;
  font-size: 4rem;
  color: white;
  font-weight: lighter;
  cursor: pointer;
}

header span:hover {
  background: rgba(3, 94, 155, 0.884);
  transform: scale(1.1);
  transition: all ease-in 0.5s;
}

form {
  display: block;
}
form span {
  color: red;
  display: block;
  font-size: 1rem;
  display: none;
}

input[type='text'] {
  font-size: 2rem;
  border-top: 0;
  border-left: 0;
  border-right: 0;
  width: 100%;
  text-transform: capitalize;
}

button,
input:focus {
  outline: none;
}

button {
  text-transform: capitalize;
  margin-top: 1rem;
  padding: 0.5rem 2rem;
  cursor: pointer;
  width: 100%;
  background: rgba(9, 119, 192, 0.884);
  color: white;
  font-size: 2.5rem;
  border-radius: 0.5rem;
}

button:hover {
  background: rgba(3, 94, 155, 0.884);
}

.todos {
  font-size: 2rem;
}

.todos h2 {
  color: rgba(9, 119, 192, 0.884);
}

ul {
  padding: 0;
  margin: 0;
}
ul li {
  display: flex;
  margin-top: 2rem;
  align-items: center;
  justify-content: space-evenly;
  transition-property: right, left;
  transition-duration: 2s;
  position: absolute;
}

li.done {
  animation: slide 1s backwards;
}

.todo-content {
  margin-left: 1rem;
  display: flex;
  width: 100%;
  justify-content: space-between;
  position: relative;
  align-items: center;
  /* align-items is optional at the end */
  top: 9px;
}

.underline {
  content: '';
  height: 2px;
  width: 100%;
  background: lightgray;
  position: absolute;
  left: 0px;
  bottom: -4px;
}

.line-thought {
  bottom: 9px;
  transition: all ease-in 0.3s;
}

.done-todo {
  color: lightgray;
}

/* animation  for  checkbox*/
.checkbox {
  -webkit-appearance: none;
  -moz-appearance: none;
  -ms-appearance: none;
  appearance: none;
  position: relative;
  top: 13.33333px;
  right: 0;
  bottom: 0;
  left: 0;
  height: 40px;
  width: 40px;
  transition: all 0.15s ease-out 0s;
  background: #cccbcb;
  border: none;
  color: rgba(9, 119, 192, 0.884);
  cursor: pointer;
  display: inline-block;
  margin-right: 0.5rem;
  outline: none;
  position: relative;
  z-index: 1000;
  border-radius: 50%;
  border-radius: 50%;
}
.checkbox:hover {
  background: #9faab7;
}
.checkbox:checked {
  background: white;
  border-radius: 0;
}
.checkbox:checked::before {
  height: 20px;
  width: 40px;
  position: absolute;
  content: '✔';
  display: inline-block;
  font-size: 36.66667px;
  text-align: center;
  line-height: 40px;
}
.checkbox:checked::after {
  border-radius: 50%;
  animation: click-wave 0.65s;
  background: rgba(9, 119, 192, 0.884);
  content: '';
  display: block;
  position: relative;
  z-index: 100;
}

/* animate checkbox when clicked */
@keyframes click-wave {
  0% {
    height: 40px;
    width: 40px;
    opacity: 0.35;
    position: relative;
  }
  100% {
    height: 200px;
    width: 200px;
    margin-left: -80px;
    margin-top: -80px;
    opacity: 0;
  }
}

/* animate li when added */
.animate {
  position: relative;
  animation-name: animatebottom;
  animation-duration: 1.2s;
}

@keyframes animatebottom {
  from {
    bottom: -50px;
    opacity: 0;
  }
  to {
    bottom: 0;
    opacity: 1;
  }
}

/* animate li when remove */
@keyframes slide {
  0% {
    left: 0px;
  }
  75% {
    opacity: 0.4;
  }

  100% {
    left: 1000px;
    opacity: 0.1;
  }
}