Вы хотите добавить padding: 0
к #login_table tr:nth-child(2) td:nth-child(2)
:
body,
html {
width: 100%;
height: 100%;
background: black;
}
#login_table {
position: relative;
top: 50%;
transform: translateY(-50%);
margin: auto;
width: 30%;
height: 50%;
font-size: 50%;
}
#login_table tr:first-child td,
#login_table tr:last-child td {
height: 10%;
background: red;
}
#login_table tr:nth-child(n+2):nth-child(-n+4) td:first-child,
#login_table tr:nth-child(2) td:nth-child(2) {
background: orange;
}
#login_table tr:nth-child(2) td:nth-child(2)::after {
content: "";
display: block;
height: 100%;
background: black;
width: 100%;
border-top-left-radius: 25px;
}
#login_table tr:nth-child(2) td:nth-child(2) {
padding: 0;
}
<table id="login_table">
<tr>
<td></td>
<td></td>
</tr>
<tr>
<td></td>
<td></td>
</tr>
<tr>
<td></td>
<td></td>
</tr>
<tr>
<td></td>
<td></td>
</tr>
</table>
Это также можно увидеть здесь .