danielcharles320

Hello,
The text for each checkbox needs to be wrapped inside an element. You could use the css sibling selector to strike through the text against the ticked checkbox.

input[type=checkbox] {
display:none;
}
input[type=checkbox] + label
{
background: #999;
height: 16px;
width: 16px;
display:inline-block;
padding: 0 0 0 0px;
}
input[type=checkbox]:checked + label
{
background: #0080FF;
text-decoration: line-through;
height: 16px;
width: 16px;
display:inline-block;
padding: 0 0 0 0px;
}
input[type=checkbox]:checked + label + label {
    text-decoration: line-through;
}

label p {
  display: inline block;
}
<div class="box">
<input type='checkbox' name='thing' value='valuable' id="thing"/><label for="thing"></label> <label>get an army</label>
<br>
<input type='checkbox' name='thing1' value='valuable2' id="thing1"/><label for="thing1"></label> <label>free the slaves</label>
<br>
<input type='checkbox' name='thing2' value='valuable3' id="thing2"/><label for="thing2"></label> <label>train my dragons</label>
<br>
<input type='checkbox' name='thing3' value='valuable4' id="thing3"/><label for="thing3"></label> <label>cross the narrow sea</label>
<br>
<input type='checkbox' name='thing4' value='valuable5' id="thing4"/><label for="thing4"></label> <label>become Queen of Westeros</label>
</div>