style.css

*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'poppins', sans-serif;
}
.container{
    width: 100%;
    height: 100vh;
    background: linear-gradient(135deg, #153677,#4e085f);
    padding: 1rem;
}
.todo{
    width: 70%;
    background: white;
    margin: 100px auto 20px;
    padding: 40px 30px 70px;
    border-radius: 10px;
    height: auto;
    display: flex;
    flex-direction: column;
    /* align-items: center; */
    justify-content: center;
}
.todo h1{
    color: #002765;
    display: flex;
    align-items: center;
    margin-bottom: 20px;
}
.todo h1 img{
    width: 30px;
    margin-left: 20px;
}
.row{
    display: flex;
    align-items: center;
    justify-content: space-between;
    background: #edeef0;
    padding-left: 20px;
    margin-bottom: 25px;
    border-radius: 10px;
}
input{
    border: none;
    outline: none;
    background: transparent;
    padding: 10px;
    flex: 1;
    font-size: 14px;
}
button{
    border: none;
    cursor: pointer;
    outline: none;
    padding: 16px 55px;
    border-radius: 40px;
    font-size: 16px;
    color: #fff;
    background: orange;
}
ul li{
    list-style: none;
    font-size: 17px;
    padding:12px 35px 12px 50px;
    cursor: pointer;
    user-select: none;
    position: relative; 
    width: 100%;
    overflow-wrap: break-word;
    text-align: justify;
}
ul li::before{
    content: '';
    position: absolute;
    height: 28px;
    width: 28px;
    border-radius: 50%;
    background-image: url(unchecked.png);
    background-size: cover;
    background-position: center;
    left: 9px;
    top:7px;
}
ul li.checked{
    color:#555;
    text-decoration: line-through;
}
ul li.checked::before{
    background-image: url(checked.png);
}
ul li span{
    right: 0;
    position: absolute;
    width: 42px;
    top:5px;
    height: 40px;
    font-size:30px;
    color:#f0160e;
    line-height: 40px;
    text-align: center;
    border-radius: 50%;
}
ul li span:hover{
    background: #edeef0;
}
@media (max-width: 600px){
    .todo{        
        margin: 50px auto 10px;
    }
    input{
        padding: 5px;        
        font-size: 15px;
        flex: 1;
    }
    button{
        padding: 16px 25px;
        border-radius: 40px;
        font-size: 16px;
    }
}
@media (max-width: 526px){
    input{
        padding: 5px;
        font-size: 12px;
        flex: 1;
    }
    button{
        padding: 10px 18px;
        font-size: 12px;     
    }
}
 @media (max-width: 448px){
     .container{
        min-width: 415px;
    } 
        input{
        padding: 9px;
        font-size: 11px;
        flex: 1;
    }
    button{
        padding: 9px 11px;
        font-size: 10px;
    }
}