6.1.4 forms.base.input-checkbox Checkboxes
If an <input> element has the type='checkbox' attribute set, the form
field is displayed as a checkbox.
It's recommended that you don't attempt to style these elements. Firefox's
implementation doesn't respect box-sizing, padding, or width.
Example
Markup: base/forms/forms-input-checkbox.twig
<span class="xml"><span class="hljs-tag"><<span class="hljs-name">div</span>></span>
<span class="hljs-tag"><<span class="hljs-name">label</span>></span><span class="hljs-tag"><<span class="hljs-name">input</span> <span class="hljs-attr">type</span>=<span class="hljs-string">"checkbox"</span> <span class="hljs-attr">class</span>=<span class="hljs-string">"</span></span></span><span class="hljs-template-variable">{{modifier_class}}</span><span class="xml"><span class="hljs-tag"><span class="hljs-string">"</span>></span> Check me out<span class="hljs-tag"></<span class="hljs-name">label</span>></span>
<span class="hljs-tag"></<span class="hljs-name">div</span>></span>
<span class="hljs-tag"><<span class="hljs-name">div</span>></span>
<span class="hljs-tag"><<span class="hljs-name">label</span>></span><span class="hljs-tag"><<span class="hljs-name">input</span> <span class="hljs-attr">type</span>=<span class="hljs-string">"checkbox"</span> <span class="hljs-attr">class</span>=<span class="hljs-string">"</span></span></span><span class="hljs-template-variable">{{modifier_class}}</span><span class="xml"><span class="hljs-tag"><span class="hljs-string">"</span> <span class="hljs-attr">value</span>=<span class="hljs-string">""</span> <span class="hljs-attr">disabled</span>></span> Option two is disabled<span class="hljs-tag"></<span class="hljs-name">label</span>></span>
<span class="hljs-tag"></<span class="hljs-name">div</span>></span>
</span>
Source:
base/forms/_forms.scss, line 158