style.css

@import url('https://fonts.googleapis.com/css2?family=Roboto:wght@300&display=swap');

* {
    box-sizing: border-box;
    padding: 0;
    margin: 0;
    font-family: 'Roboto', sans-serif;
}

body, html{
    width: 100%;
    height: 100%;
}

body {
    display: flex;
    justify-content: flex-start;
    flex-wrap: wrap; 
}

.day {
    height: 100%;
    width: 100%;
    position: relative;
}

.monday {
    background: #E36F6F;
}

.tuesday {
    background: #FFC06D;
}

.wednesday {
    background: #8AE3FF;
}

.thursday {
    background: #ABE7D0;
}

.friday {
    background: #8DFF95;
}

.saturday {
    background: #CA8DFF;
}

.sunday {
    background: #E36ABE;
}

.add {
    z-index: 1;
    background-image: url(img/plus.svg);
}

.add, .edit, .reset{
    cursor: pointer;
    width: 45px;
    height: 45px;
    border-radius: 50%;
    border: 2px solid #111;
    position: fixed;
    bottom: 20px;
    right: 20px;
    background-color: #111;
    background-repeat: no-repeat;
    background-size: 32px;
    background-position: center;
    transition: border .3s ease, transform .3s ease, bottom .3s ease;
}

.add:hover, .edit:hover, .reset:hover {
    border: 2px solid #FEFEFE;
}

.edit, .reset {
    bottom: 23px;
    right: 23px;
    width: 38px;
    height: 38px;
    background-size: 22px;
    z-index: 0;
}

.edit {
    background-image: url(img/pen.svg);
    background-size: 18px;
}

.reset {
    background-image: url(img/reset.svg);
}

.rotate {
    transform: rotate(45deg);
}

.showEdit {
    bottom: 70px;
}

.showReset {
    bottom: 115px;
}

.title {
    width: 100%;
    text-align: center;
    font-size: 3em;
    padding: 1em;
    font-weight: 200;
    letter-spacing: 7px;
    color: #FEFEFE;
}

.content {
    position: absolute;
    left: 50%;
    top: 55%;
    transform: translate(-50%,-50%);
    height: 60%;
    width: 80%;
    overflow-y: auto;
    padding: 0 5px;
}

*::-webkit-scrollbar {
    width: 7px;
    background-color: #111111ad;
    border-radius: 20px;
}

*::-webkit-scrollbar-thumb {
    background-color: #111;
}

textarea::-webkit-scrollbar {
    background-color: #686868;
}

textarea::-webkit-scrollbar-thumb {
    background-color: #FEFEFE;
    border-radius: 10px;
}

.task {
    width: 100%;
    max-width: 500px;
    height: 15%;
    min-height: 60px;
    border: 2px solid #111;
    background-color: #111;
    padding: 1em;
    border-radius: 5px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    position: relative;
    z-index: 1;
    overflow: hidden;
    transition: border .3s ease, background-color .4s;
    margin-bottom: 1em;
    position: relative;
}

.task:hover {
    border: 2px solid #FEFEFE;
}

.task span {
    color: #FEFEFE;
    letter-spacing: 2px;
    width: 85%;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.completed {
    background-color: #8DFF95;
    background-image: url(img/check.svg);
    position: absolute;
    top: 0;
    bottom: 0;
    right: 0;
    height: 100%;
    cursor: pointer;
    width: 50px;
    background-size: 20px;
    background-repeat: no-repeat;
    background-position: center;
    transition: transform .4s ease, background-size .4s ease, background-color .4s ease;
    z-index: 2;
    border-top-right-radius: 3px;
    border-bottom-right-radius: 3px;
}

.windowAddTask, .windowConfirm{
    max-width: 500px;
    position: fixed;
    background: #111;
    top: 57%;
    left: 50%;
    transform: translate(-50%, -50%);
    opacity: 0;
    z-index: -1;
    width: 75%;
    display: flex;
    flex-direction: column;
    align-items: center;
    
    border-radius: 5px;
    transition: opacity .5s ease, top .5s ease;
}

.windowConfirm {
    padding: 1em;
}

.windowConfirm span {
    color: #FEFEFE;
}

.windowConfirm > div {
    width: 100%;
    display: flex;
    justify-content: space-between;
}

.windowConfirm button {
    margin-top: 1.3em;
    padding: .5em 1em;
    width: 45%;
    border: none;
    color: #FEFEFE;
    cursor: pointer;
    letter-spacing: 1px;
    border-radius: 5px;
}

.btnYes {
    background: #8DFF95BA;
}

.btnNo {
    background: #E36F6FBA;
}

.showWindow {
    z-index: 2;
    opacity: 1;
    top: 50%;
}

.viewAllTask {
    width: 90%;
    overflow: hidden;
    border: 1.5px solid #FEFEFE;
}

.viewAllTask > .close {
    position: absolute;
    top: 10px;
    right: 10px;
    cursor: pointer;
}

.viewAllTask > .delTask {
    position: absolute;
    bottom: 0px;
    right: 0px;
    cursor: pointer;
    background-color: #E36F6F;
    padding: .3em;
    transition: padding .3s ease;
    border-top-left-radius: 10px;
}

.viewAllTask > .delTask:hover {
    padding: .5em;
}


.windowAddTask textarea, .viewAllTask textarea {
    width: 83%;
    margin-top: 1.5em;
    margin-left: -15px;
    margin-bottom: 20px;
    outline: none;
    background-color: #111;
    border: none;
    border-left: 2px solid #FEFEFE;
    color: #FEFEFE;
    padding: .5em;
    resize: none;
    padding-left: 1.5em;
    font-family: 'Roboto', sans-serif;
    letter-spacing: 3px;
}

.viewAllTask textarea {
    height: 100px;
    padding-left: 1em;
}

.checkboxes {
    display: grid;
    grid-template-columns: 1fr 1fr;
    width: 100%;
    margin-left: 25%;
}

.windowAddTask input[type="checkbox"] {
    width: 0;
    height: 0;
}

.windowAddTask input[type="checkbox"] + label {
    position: relative;
    margin-left: 10px;
    cursor: pointer;
    color: #FEFEFE;
    width: 100px;
}

.windowAddTask input[type="checkbox"] + label::after {
    content: "";
    height: 10px;
    width: 10px;
    border: 2px solid #FEFEFE;
    display: inline-block;
    position: absolute;
    top: 50%;
    left: -25px;
    z-index: 2;
    cursor: pointer;
    transform: translateY(-50%);
}

.windowAddTask input[type="checkbox"] + label::before {
    content: "";
    height: 0px;
    width: 0px;
    background: #8DFF95BA;
    display: inline-block;
    position: absolute;
    top: 50%;
    left: -23px;
    z-index: 2;
    cursor: pointer;
    transform: translateY(-50%);
    transition: width .4s ease, height .4s ease;
}

.windowAddTask input[type="checkbox"]:checked + label::before {
    width: 10px;
    height: 10px;
}

.buttons {
    margin: 1em;
    margin-top: 1.5em;
    width: 100%;
    display: flex;
    justify-content: space-around;
}

.buttons button {
    padding: 1em;
    border: none;
    cursor: pointer;
    background: transparent;
    color: #FEFEFE;
    letter-spacing: 1px;
    border-radius: 5px;
}

.buttons button:nth-child(1) {
    background: #8DFF95BA;
}

.buttons button:nth-child(2) {
    color: #E36F6F;
}

@media screen and (min-width: 555px) {
    .buttons button {
        width: 45%;
    }

    .content {
        display: grid;
        justify-items: center;
        grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
        grid-template-rows: repeat(auto-fit, 65px);
        grid-gap: 20px;
    }

    .task span {
        width: 80%;
    }
}

@media screen and (min-width: 755px) {

    .content {
        width: 65%;   
    }

}