CSS Box/shadow overlapping issue z-index

Question

Please take a look at the code snippet: http://codepen.io/anon/pen/JItLa

I'm trying to show 2 rows of blocks with different amount of items in a row. The hover event should reveal the CSS shadow, but there is a problem: the right border of the shadow is overlapped with the next block. You would say the possible solution here is to use display:inline-block which leaves the gaps between the blocks, but I don't need the gaps. The blocks should stay sticky to each other but the right shadow should overlap the next block onhover.

html,
body {
  margin: 0;
  padding: 0
}
.wrapper {
  width: 100%;
  margin-top: 20px
}
.tile,
.tile2 {
  float: left;
  background: #f2f2f2
}
.tile {
  width: 25%
}
.tile2 {
  width: 33.3%;
  border-left: 1px solid #ddd
}
.tile:hover,
.tile2:hover {
  -webkit-box-shadow: 0 0 2px rgba(255, 255, 190, .75), 0 0 23px 1px #000;
  -moz-box-shadow: 0 0 2px rgba(255, 255, 190, .75), 0 0 23px 1px #000;
  box-shadow: 0 0 2px rgba(255, 255, 190, .75), 0 0 23px 1px #000
}
.header {
  padding: 20px 0px 10px;
  text-align: center
}
.clear {
  clear: both
}

<div class="wrapper">
  <div class="tile">
    <div class="header">some text</div>
  </div>
  <div class="tile">
    <div class="header">some text</div>
  </div>
  <div class="tile">
    <div class="header">some text</div>
  </div>
  <div class="tile">
    <div class="header">some text</div>
  </div>
  <div class="clear"></div>
</div>
<div class="wrapper">
  <div class="tile2">
    <div class="header">some text</div>
  </div>
  <div class="tile2">
    <div class="header">some text</div>
  </div>
  <div class="tile2">
    <div class="header">some text</div>
  </div>
  <div class="clear"></div>
</div>

How is that possible?

There is another problem here: when I add the border between the blocks the last blocks moves to the next line which is not OK. See the 2nd row in the example given above.

Answer 1

Add a z-index to the element on hover.

Additionally, the element also has to be positioned in order for the z-index property to work. Therefore add position:relative too.

9.9.1 Specifying the stack level: the 'z-index' property

z-index: Applies to: positioned elements

Each box has a position in three dimensions. In addition to their horizontal and vertical positions, boxes lie along a "z-axis" and are formatted one on top of the other. Z-axis positions are particularly relevant when boxes overlap visually. This section discusses how boxes may be positioned along the z-axis.

Updated Codepen - it works now.

.tile:hover, .tile2:hover {
    z-index: 1;
    position: relative;
}

To address your second issue, the elements are appearing on a new line because their widths do not add up, as it is 1px off due to the border.

33.3% + 33.3% + 33.3% + 1px != 100%

You have a few different options:

• Use calc() to subtract 1px from the width - width: calc(33.3% - 1px)

• Change the box model to include the border in the element's width calculation - box-sizing

If you choose to use box-sizing, you need appropriate vendors/prexes if you want support across all browsers. I would use something like:

.tile2 {
    width: 33.3%;
    border-left: 1px solid #ddd;
    box-sizing: border-box;
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
}

Updated Codepen using box-sizing.