style.css

* {
    font-family: Vazir;
    direction: rtl;
}
body {
    background-color: #35363a;
    /*color: #fff;*/
}
.heading {
    width: 50%;
    margin: 30px auto;
    text-align: center;
    color: #fff;
}
form {
    width: 35%;
    margin: 30px auto;
    border-radius: 5px;
    padding: 10px;
    border: 2px solid #fff;
    border-radius: 18px;
}
form p {
    color: red;
    margin: 0px;
}
.task_input {
    width: 75%;
    height: 15px;
    padding: 10px;
    margin: 5px;
    border: 2px solid #fff;
    border-radius: 18px;
    background-color: #35363a;
    color: #fff;
}
.add_btn {
    height: 39px;
    background: #7a7777e0;
    color: #fff;
    border: 3px solid #fff;
    border-radius: 18px;
    padding: 5px 20px;
}
table {
    width: 50%;
    margin: 30px auto;
    border-collapse: collapse;
}
tr {
    border-bottom: 1px solid #cbcbcbad;
}
.tr-c {
    color: #fff;
}
th {
    font-size: 19px;
    color: #ee5353;
}
th, td {
    border: none;
    height: 30px;
    padding: 2px;
}
.task {
    text-align: left;
}
.delete {
    text-align: center;
}
.delete a {
    color: white;
    background: #a52a2a;
    padding: 1px 6px;
    border-radius: 18px;
    text-decoration: none;
}
a {
    text-decoration: none;
}
.add_btn {
    cursor: pointer;
    padding: 10px;
    margin: 5px;
}