Transform Scale Causing Gaps/Lines

Question

I'm building a website currently and am experiencing issues with transform: scale. I've got a button, and when a user hovers over it, two things happen:

1. A background "sweeps" in diagonally
2. The button label colour changes
3. The button grows slightly

I have got this working, and it looks really nice, but after implementing point 3, I'm seeing a weird gap to the left hand side when the button grows.

Here is my code: click for demo

HTML

<a href="#" class="button">Hover</a>

CSS

body {
    text-align: center;
    padding-top: 10%;
}

.button {
    display: inline-block;
    text-transform: uppercase;
    font-size: 1.1em;
    font-weight: 600;
    background: transparent;
    transition: all ease .25s;
    border: 3px solid green;
    color: green;
    position: relative;
    overflow: hidden;
    z-index: 2;
    font-family: sans-serif;
    padding: 20px 35px;
    text-decoration: none;
}

.button:before {
    content: ' ';
    transition: all ease-out .25s;
    width: 200%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
    transform-origin: 0 0;
    z-index: -1;
    transform: skewX(-45deg) translateX(-100%);
    background: green;
}

.button:hover:before {
    transform: translateX(0);
}

.button:hover {
  color: white;
  transform: scale(1.1);
}

And here's a screenshot of the gap I'm seeing. This issue occurs in Chrome and Safari (I haven't tested Firefox or IE as I can't download them at work).

Screenshot of weird gap

Answer 1

It "only" appears in Chrome but not Firefox (edit: worse in Edge: first it's on the left then on bottom...). Not sure if a rounding error or something else is the cause of that gap, but I find that replacing border by a box-shadow improves the rendering.
There's still a gap that can be seen near the end of the transition but finally disappears so I added 2 box-shadows on :hover: the new one is inset and fills the gap between "border/box-shadow" and content box faster.

Codepen: http://codepen.io/PhilippeVay/pen/oYjZzK?editors=0100

body {
    text-align: center;
    padding-top: 10%;
}

.button {
    display: inline-block;
    text-transform: uppercase;
    font-size: 1.1em;
    font-weight: 600;
    background: transparent;
    transition: all ease .25s;
    box-shadow: 0 0 0 3px green; /* replaces border which caused a gap in Chr, not Fx */
    color: green;
    position: relative;
    overflow: hidden;
    z-index: 2;
    font-family: sans-serif;
    padding: 19px 34px;
    text-decoration: none;
}

.button:before {
    content: ' ';
    transition: transform ease-out .25s;
    width: 200%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
    transform-origin: 0 0;
    z-index: -1;
    transform: skewX(-45deg) translateX(-100%);
    background: green;
}

.button:hover:before {
    transform: translateX(0);
}

.button:hover {
  color: white;
  box-shadow: 0 0 0 3px green, inset 0 0 0 1px green; /* improves end of transition in Chrome */
  transform: scale(1.1);
}

<a href="#" class="button">Hover</a>

EDIT: playing with the size of the transitioned :pseudo

.button:before {
  content: ' ';
  transition: all ease-out .25s;
  width: calc(200% + 6px);
  height: calc(100% + 6px);
  position: absolute;
  top: -3px;
  left: -3px;
  transform-origin: 0 3px;
  z-index: -1;
  transform: skewX(-45deg) translateX(-100%);
  background: green;
}

to take into account the border but that doesn't change anything because of overflow: hidden.

So here's my third try: by adding a container (or having the A element as a container) and keeping the border on the child element, it makes that gap disappear (overflow is around the border).

Codepen: http://codepen.io/PhilippeVay/pen/ZBbKWd

body {
    text-align: center;
    padding-top: 10%;
}
a {
  display: inline-block;
  overflow: hidden;
    background: transparent;
    transition: all ease .25s;
    color: green;
    position: relative;
    z-index: 2;
    font-family: sans-serif;
    text-decoration: none;
}
a > span {
    display: inline-block;
    text-transform: uppercase;
    font-size: 1.1em;
    font-weight: 600;
    border: 3px solid green;
    padding: 20px 35px;
}

a:before {
    content: ' ';
    transition: all ease-out .25s;
    width: 200%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
    transform-origin: 0 0;
    z-index: -1;
    transform: skewX(-45deg) translateX(-100%);
    background: green;
}

a:hover:before {
    transform: translateX(0);
}

a:hover {
  color: white;
  transform: scale(1.1);
}

<a href="#" class="button"><span class="bd">Hover</span></a>

Fx transitions till the end flawlessly... and "corrects" the width by adding 2px on the right. But it's already visible in your jsbin so it's another story (and less annoying I guess as user will have clicked by then imho)