Drawing responsive Tic Tac Toe board in pure (no JS) HTML & CSS

Question

I'm solving HTML layout problem similar to drawing responsive Tic Tac Toe board in HTML + CSS and without any JS. Here is how I define the board's layout:

<div class="board">
    <div class="lines">
        <div class="line">
            <div class="cell">
                <div class="cell-content"></div>
            </div>
            <div class="cell">
                <div class="cell-content"></div>
            </div>
            <div class="cell">
                <div class="cell-content"></div>
            </div>
        </div>
        <div class="line">
            <div class="cell">
                <div class="cell-content"></div>
            </div>
            <div class="cell">
                <div class="cell-content"></div>
            </div>
            <div class="cell">
                <div class="cell-content"></div>
            </div>
        </div>
        <div class="line">
            <div class="cell">
                <div class="cell-content"></div>
            </div>
            <div class="cell">
                <div class="cell-content"></div>
            </div>
            <div class="cell">
                <div class="cell-content"></div>
            </div>
        </div>
    </div>
</div>

and here is the corresponding CSS:

.board {
    position: relative;
    height: 100%;
    width: 100%;
    border:1px solid black;
    box-sizing:border-box;
}
.board:before {
    content:"";
    display: block;
    padding-top: 100%;
}
.lines {
    position: absolute;
    top: 0;
    left: 0;
    bottom: 0;
    right: 0;
}
.line {
    width: 100%;
}
.cell {
    float: left;
    width: 33.3333%;
    border:1px solid black;
    box-sizing:border-box;
}
.cell:before {
    content:"";
    display: block;
    padding-top: 100%;
}
.cell-content {
    position: absolute;
    top: 0;
    left: 0;
    bottom: 0;
    right: 0;
}

Here I do not set any sizes besides width: 33.3333%. The height of the board and fields is set using the Height equals width with pure CSS approach.

And I would note that almost everything is great. The only problem here: sometimes the sum of widths/heights of board cells are less than the width/height of the board. It means that I can see the gap between last field border and the board border. I can reproduce it with Chrome or FF, but it never happens in IE. Is there a way to fix this?

The demo is available on the jsfiddle (the red line is what I'm trying to get rid of)

UPDATE: It happens in IE also, not sure why I did not saw it before.

Answer 1

Simple Fix is to give the .line Elements overflow: auto;

.line {
    overflow: auto;
}

and your good to go :D