style.css

*,
*::before,
*::after{
    padding: 0;
    margin: 0;
    box-sizing: border-box;
}

body{
    height: 100vh;
    background: #066acd;
    font-family: 'poppins', sans-serif;
}

.container{
    width: 40%;
    min-width: 450px;
    position: absolute;
    transform: translate(-50%, -50%);
    top: 50%;
    left: 50%;
    background: #fff;
    border-radius: 10px;
}

#newtask{
    position: relative;
    padding: 30px 20px;
    overflow: hidden;
}

#newtask input{
    width: 100%;
    height: 45px;
    font-size: 15px;
    border: 2px solid #d1d3d4;
    padding: 12px;
    border-radius: 5px;
    color: #111111;
    font-weight: 500;
    position: relative;
    transition: 0.3s ease;
}

#newtask input:focus{
    outline: none;
    border-color: #0d75ec;
}

#newtask button{
    position: relative;
    float: right;
    width: 20%;
    height: 45px;
    border-radius: 5px;
    border: none;
    outline: none;
    background-color: #0d75ec;
    color: #fff;
    font-size: 16px;
    font-weight: 500;
    cursor: not-allowed;
    margin-right: -1000px; /*big number to avoid anomaly in bigger screen*/
    transition: 0.3s ease;
    opacity: 0.6;
}

#newtask button.active{
    opacity: 1;
    cursor: pointer;
}

/*Animate the button and text area*/

 .container:hover #newtask button{
    margin-right: 0;
}

.container:hover #newtask input{
    width: 75%;
}

/* task addition part */
#tasks{
    background-color: #fff;
    padding: 30px 20px;
    margin-top: 10px;
    border-radius: 10px;
    width: 100%;
    position: relative;
}

.task{
    background-color: #c5e1e6;
    height: 50px;
    margin-bottom: 8px;
    padding: 5px 10px;
    display: flex;
    border-radius: 5px;
    align-items: center;
    justify-content: space-between;
    border: 1px solid #939697;
    overflow: hidden;
}

.task span{
    font-size: 15px;
    font-weight: 400;
}

.task button{
    background-color: #0a2ea4;
    color: #fff;
    height: 100%;
    width: 40px;
    border-radius: 5px;
    border: none;
    outline: none;
    transition: 0.2s ease;
    margin-right: -50px;
}

.task button:hover{
    background-color: #fff;
    color:#0a2ea4;
    cursor: pointer;
}

.container:hover .delete{
    margin-right: 0;
}

/* footer */

footer{
    text-align: center;
    opacity: 10%;
    margin-bottom: 15px;
    font-size: 12px;
}