*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Poppins', sans-serif;
}
.container{
    width: 100%;
    min-height: 100vh;
    background: linear-gradient(135deg, #71b7e6, #9b59b6);
    padding: 10px;
}
.to-do-app{
    width: 100%;
    max-width: 540px;
    background-color: #fff;
    margin: 100px auto 20px;
    padding: 40px 30px 70px;
    border-radius: 10px;    
}
.to-do-app h2{
  color: #9b59b6;
  display: flex;
  align-items: center;
  margin-bottom: 20px;
}
.to-do-app h2 img{
    width: 30px;
    margin-left: 10px;
}
.row{
    display: flex;
    align-items: center;
    justify-content: space-between;
    background-color: #f0f0f0;
    border-radius: 10px;
    padding-left: 20px;
    margin-bottom: 25px;

}
input{
    flex: 1;
    border: none;
    outline: none;
    background: transparent;
    padding: 10px;
}
button{
    border: none;
    outline: none;
    padding: 10px 50px;
    background-color: #ff5945; 
    color: #fff;
    font-size: 16px;
    cursor: pointer;
    border-radius: 40px;
}
ul li{
    list-style: none;
    font-size: 17px;
    padding: 12px 8px 12px 50px;
    user-select: none;
    cursor: pointer;
    position: relative;
}
ul li::before{
    content: '';
    position: absolute;
    height: 28px;
    width: 28px;
    border-radius: 50%;
    background-image: url('img/uncheck.png'); /* uncheck */
    background-size: cover;
    background-position: center;
    top: 12px;
    left: 8px;
}

ul li.checked{
    color: #9b59b6;
    text-decoration: line-through;
}

ul li.checked::before{
    background-image: url('img/check.png');   /* check */
}