Border opacity in css using rgba() not working

Question

I am working on a simple login site template using html and css (no js yet) and for some reason when I use the border-color property in my css for the .main class and i use the rgba() function like this: border-color: rgba(255, 255, 255, 0.5); the rgb works but the alpha does not at all.

I tried doing this instead and i also removed the original line: border: 60px solid rgba(255, 255, 255, 0.5);

I am using chrome version 108.

html {
  height: 100%;
  width: 100%;
  font-family: Arial, Helvetica, sans-serif;
  background-image: linear-gradient(red, lime);
}

.main {
  margin: 60px;
  border: 60px solid;
  border-color: rgba(255, 255, 255, 0.5) !important;
  /* Set border opacity */
  border-radius: 30px;
  background-color: rgba(255, 255, 255, 0.8);
}

.main input {
  border-radius: 10px;
  height: 30px;
  background-color: lightgray;
}

.main input:focus {
  background-color: white;
}

.main button {
  height: 30px;
  border-radius: 15px;
}

<center>
  <div class="main">
    <h1>Login</h1>
    <p>Hello! To continue please log into our service:</p>
    <h2>Email</h2>
    <input type="email">
    <h2>Password</h2>
    <input type="password">
    <br>
    <br>
    <button type="button" onclick='alert("logging in...")'>Login</button>
  </div>
</center>

Answer 1

You need to add background-clip: padding-box; to limit the background to padding area and not have it under your border-color:

html {
  height: 100%;
  width: 100%;
  font-family: Arial, Helvetica, sans-serif;
  background-image: linear-gradient(red, lime);
}

.main {
  margin: 60px;
  border: 60px solid;
  border-color: rgba(255, 255, 255, 0.5);
  /* Set border opacity */
  border-radius: 30px;
  background-color: rgba(255, 255, 255, 0.8);
  background-clip: padding-box
}

.main input {
  border-radius: 10px;
  height: 30px;
  background-color: lightgray;
}

.main input:focus {
  background-color: white;
}

.main button {
  height: 30px;
  border-radius: 15px;
}

<div class="main">
    <h1>Login</h1>
    <p>Hello! To continue please log into our service:</p>
    <h2>Email</h2>
    <input type="email">
    <h2>Password</h2>
    <input type="password">
    <br>
    <br>
    <button type="button" onclick='alert("logging in...")'>Login</button>
  </div>