Box-shadow Inset fill leaving unfilled edges?

Issue

I am using a css transition to fill my buttons during hover using box-shadow inset.

I am also using the transition to alter border-radius of the button during hover.

When I hover, the transition happens, but I am left with a thin unfilled curved line on each inner-corner of the button.

HTML

  <div class="container">
  <button type="button" id="upSwipe">Up Swipe</button>
  <button type="button" id="downSwipe">Down Swipe</button>
  <button type="button" id="leftSwipe">Left Swipe</button>
  <button type="button" id="rightSwipe">Right Swipe</button>
</div>

CSS:

* {
  margin: 0;
  padding: 0;
  background: none;
}

.container {
  position: absolute;
  background: black;
  background-size: cover;
  height: 100vh;
  width: 100vw;
  
  display: flex;
  flex-direction: row;
  flex-wrap: wrap;
  justify-content: center;
  align-items: center;
}

button {
  height: 200px;
  width: 200px;
  
  margin: 20px;
  
  background: none;
  border: 10px solid orange;
  border-radius: 20px;
  
  color: orange;
  font-size: 30px;
  
  box-shadow: inset 0 0 0 orange;
  
  transition: 0.5s ease;
}

#upSwipe:hover {
  box-shadow: inset 0 -7em 0 orange;
  color: black;
  border-radius: 30px;
}
* {
  margin: 0;
  padding: 0;
  background: none;
}

.container {
  position: absolute;
  background: black;
  background-size: cover;
  height: 100vh;
  width: 100vw;
  
  display: flex;
  flex-direction: row;
  flex-wrap: wrap;
  justify-content: center;
  align-items: center;
}

button {
  height: 200px;
  width: 200px;
  
  margin: 20px;
  
  background: none;
  border: 10px solid orange;
  border-radius: 20px;
  
  color: orange;
  font-size: 30px;
  
  box-shadow: inset 0 0 0 orange;
  
  transition: 0.5s ease;
}

#upSwipe:hover {
  box-shadow: inset 0 -7em 0 orange;
  color: black;
  border-radius: 30px;
}

Solution

1. You need to change the border-radius from button.
2. Remove the border-radius on hover.

removing border-radius on hover alone will not fix the issue, you can either increase the border size of button or decrease the border-radius of the button.

* {
  margin: 0;
  padding: 0;
  background: none;
}

.container {
  position: absolute;
  background: black;
  background-size: cover;
  height: 100vh;
  width: 100vw;
  display: flex;
  flex-direction: row;
  flex-wrap: wrap;
  justify-content: center;
  align-items: center;
}

button {
  height: 200px;
  width: 200px;
  margin: 20px;
  background: none;
  border: 10px solid orange;
  border-radius: 10px;
  color: orange;
  font-size: 30px;
  transition: 0.5s ease;
}

#upSwipe:hover {
  box-shadow: inset 0 -7em 0 orange;
  color: black;
}

#downSwipe:hover {
  box-shadow: inset 0 7em 0 orange;
  color: black;
}

#leftSwipe:hover {
  box-shadow: inset 7em 0 0 orange;
  color: black;
}

#rightSwipe:hover {
  box-shadow: inset -7em 0 0 orange;
  color: black;
}

<div class="container">
  <button type="button" id="upSwipe">Up Swipe</button>
  <button type="button" id="downSwipe">Down Swipe</button>
  <button type="button" id="leftSwipe">Left Swipe</button>
  <button type="button" id="rightSwipe">Right Swipe</button>
</div>

Answered By - Manjuboyz