style.css

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

body {
    min-height: 100vh;
    width: 100%;
}

.counter {
    height: 100%;
    width: 100%;
    display: flex;
}

.counter .left_side {
    width: 25%;
    height: 100%;
    padding: 15px 0;
    border-right: 1px solid black;
    flex-direction: column;
}

.counter .left_side .addNoteBtn {
    width: 90%;
    margin: 15px 5%;
    padding: 10px 25px;
    font-size: 20px;
    border: none;
    outline: none;
    border-radius: 10px;
    background: #00af8c;
    color: #fff;
    font-weight: bold;
    cursor: pointer;
}

.counter .left_side .addNoteBtn:hover {
    color: #000;
}

.counter .left_side .noteList_item {
    width: 90%;
    border-radius: 10px;
    padding: 10px;
    margin: auto;
    margin-bottom: 10px;
    background: #eeeeee;
    cursor: pointer;
}

.counter .left_side .noteList_item:hover {
    background: #d0d0d0;
}

.counter .left_side .noteList_item .noteList_item_title {
    color: #000;
    font-size: 25px;
}

.counter .left_side .noteList_item .noteList_item_body {
    color: #000;
    margin: 20px 0;
}

.counter .left_side .noteList_item .noteList_item_bottom {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.counter .left_side .noteList_item .noteList_item_bottom .noteList_item_bottom_btn_area {
    display: flex;
    gap: 25px;
}
.counter .left_side .noteList_item .noteList_item_bottom .noteList_item_bottom_btn_area .noteList_item_btn {
    width: 20px;
}

.counter .left_side .noteList_item .noteList_item_bottom .noteList_item_time {
    color: #000;
}

.counter .right_side {
    width: 75%;
    height: 100%;
}

.counter .right_side.hide {
    visibility: hidden;
}

.counter .right_side .title_and_btn{
    display: flex;
}

.counter .right_side .title_and_btn .btn_area {
    width: 10%;
    display: flex;
    align-items: center;
    justify-content: space-evenly;
    background: #d0d0d0;
    border-radius: 10px;
}

.counter .right_side .title_and_btn .btn_area .btn {
    width: 25px;
    cursor: pointer;
}

.counter .right_side .title_and_btn .note_title {
    width: 90%;
    border: none;
    outline: none;
    font-size: 25px;
    padding: 20px;
    font-weight: bold;
    color: #00af8c;
}

.counter .right_side .note_body {
    height: 100%;
    width: 100%;
    border: none;
    outline: none;
    font-size: 25px;
    padding: 10px 20px;
}