Centering radio buttons (flexbox?)

Issue

I'm trying to horizontally and vertically center some radio buttons: http://jsfiddle.net/yxxd0cht/

I was thinking of using a flexbox or something like that, but I couldn't get it to work.

The CSS:

.costs
{
font-family: Arial, sans-serif;
background-color:#FFBC02;
color:white;
padding: 5px 12px;
margin-left:5px;
font-size: 1.05em;
}

input[type=radio]
{
display:none;
}

The HTML:

<div id="green">
<fieldset id="costs">
                <legend>Costs: </legend>
                <input id="free" name="costs" type="radio" value="free">
                <label class="costs" for="free">Free</label>

                <input id="chargeable" name="costs" type="radio" value="chargeable">
                <label class="costs" for="chargeable">Chargeable</label>

                <input id="mixed" name="costs" type="radio" value="mixed" checked>
                <label  class="costs" for="mixed">Mixed</label>
                </fieldset>
</div>

Solution

If you're open to using flexbox, and you're using HTML5 syntax, I assume your browser requirements would allow you to use another strategy as well. This is my favorite way of precisely centering an element of unknown dimensions inside a container of unknown dimensions.

Note that I cleaned up the markup as well--since you're not using any JavaScript that requires you to precisely identify items by their class or ID, the only ID that you really care about is that of the #green div. The remaining elements can be easily addressed by using element-level selectors, which helps you avoid over-specifying styles and makes long-term maintenance easier.

#green {
  background-color: green;
  height: 200px;
  /* Make this the positioning parent for fieldset */
  position: relative;
}
#green label {
  font-family: Arial, sans-serif;
  background-color: #FFBC02;
  color: white;
  padding: 5px 12px;
  margin-left: 5px;
  font-size: 1.05em;
}
#green input[type=radio] {
  display: none;
}
#green input[type=radio]:checked + label {
  background-color: lightgreen;
}
#green fieldset {
  /* Border added for visualization */
  border: 1px solid red;
  /* Position absolute will position relative to first
  non-static ancestor (in this case, #green) */
  position: absolute;
  /* Positions fieldset's top/left corner exactly in the
  center of #green */
  top: 50%;
  left: 50%;
  /* Translate's percentages are based on dimensions of 
  the element, not the width of the container, like 
  CSS % units. */
  transform: translate(-50%, -50%);
}

<!-- Removed unnecessary classes & IDs throughout.
The elements are easily addressible in CSS styles using 
#green as the parent. -->
<div id="green">
  <fieldset>
    <legend>Costs:</legend>
    <input id="free" name="costs" type="radio" value="free">
    <label for="free">Free</label>

    <input id="chargeable" name="costs" type="radio" value="chargeable">
    <label for="chargeable">Chargeable</label>

    <input id="mixed" name="costs" type="radio" value="mixed" checked>
    <label for="mixed">Mixed</label>
  </fieldset>
</div>

Answered By - Palpatim