style.css

*{
    margin: 0;
    padding: 0;
}
body{
    height: 100%;
    background-color: rgb(0, 0, 0);
}
.image{
    width: 15rem;
    height:10rem;
    margin-top: auto;
    margin-left: 40rem;
   display: flex;
}
#input_div{
    display: flex;
	justify-content: center;
	align-items: center;
}
#input_div .todo{
    padding: 0.5rem 1rem;
    outline: none;
    border: none;
    height: 50px;
    border-radius: 25px;
    width: 400px;
    margin: 0.25rem;
    transition: .5s;
    font-size: 1.15rem;
}
#btn{
    height: 70px;
    width: 70px;
    border-radius: 25px;
    outline: none;
    border: none;
    background-color: rgb(226, 161, 41);
    color: #fff;
    font-size: 1.15rem;
    margin: 0.25rem;
    transition: .5s;
    cursor: pointer;
}
#btn:hover{
    opacity: 0.7;
}
.container{
    display: flex;
	flex-direction: column;
	justify-content: center;
	align-items: center;
	text-align: center;
	margin-top: 2rem;
}

.task{
    padding: 0.5rem;
	border-bottom: 4px solid #fff;
	margin-bottom: 1.5rem;
}
.task span{
    background: none;
	outline: none;
	border: none;
	color: #fff;
	font-size: 1.4rem;
	width: 245px;
}
.task button{
    height: 50px;
    width: 75px;
    border-radius: 25px;
    outline: none;
    border: none;
    background-color: rgb(226, 161, 41);
    color: #fff;
    font-size: 1.15rem;
    margin-left: 340px;
    
    cursor: pointer;
}
.completed{
    text-decoration: line-through;
   cursor: pointer;
    
}
@media only screen and (max-width:700px){
    .image{

    width: 15rem;
    height:10rem;
    margin: auto;
   
    }
   
    #input_div .todo{
       
        height: 30px;
       
        width: 250px;
        font-size: 1rem;
       
    }
    #btn{
        height: 50px;
        width: 50px;
       font-size: 1rem;
    }
    .container{
        margin:10px;
    }
    .task{
        height: 30px;
       width: 300px;
        font-size: 1rem;
    }
    
    .task button{
        height: 40px;
        width: 40px;
        margin-left:auto;
        font-size: 1rem;
    }
    

}