JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE HTML
     PUBLIC "-//W3C//DTD HTML 4.01//EN"
     "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
    <link rel="stylesheet" href="stile.css"/>
    <title></title>
            <table id="tableau">
            <thead>
                <tr id="first_row">
                    <td id="result"></td>
                    <td class="second_col"><input type="text" class="cell" value="3" /></td>
                    <td><input type="text" class="cell" value="1"/></td>
                    <td><input type="text" class="cell" value="0"/></td>
                    <td><input type="text" class="cell" value="0"/></td>
                    <td><input type="text" class="cell" value="0"/></td>
                </tr>
            </thead>
            <tbody>
                <tr>
                    <td><input type="text" class="cell" value="9"/></td>
                    <td class="second_col"><input type="text"value="1" /></td>
                    <td><input type="text" class="cell" value="1"/></td>
                    <td><input type="text" class="cell"value="1" /></td>
                    <td><input type="text" class="cell"value="0" /></td>
                    <td><input type="text" class="cell"value="0" /></td>
                </tr>
                <tr>
                    <td><input type="text" class="cell"value="6" /></td>
                    <td class="second_col"><input type="text" value="1" /></td>
                    <td><input type="text" class="cell" value="0"/></td>
                    <td><input type="text" class="cell"value="0" /></td>
                    <td><input type="text" class="cell"value="1" /></td>
                    <td><input type="text" class="cell"value="0" /></td>
                </tr>
                <tr>
                    <td><input type="text" class="cell"value="5" /></td>
                    <td class="second_col"><input type="text" value="0" /></td>
                    <td><input type="text" class="cell" value="1"/></td>
               ...

CSS

table {
     border-collapse: collapse;
     border: 1px solid #CCCCCC;
}

tr td {
    padding: 0;
     border: 1px solid #CCCCCC;
     margin: 1em;
}

.main {
     border: 3px dotted blue;
     margin: 0pt auto;
     padding: 2em;
     width: 50em;
}

input {
     border: 0pt none;
     font-size: 1em;
     height: 2.5em;
     text-align: center;
     width: 5em;
}

thead input {
     background-color: violet;
}

#first_row {
     border-bottom: 1em solid #CCCCCC;
}

.second_col {
     border-left: 1em solid #CCCCCC;
}