<div class="container">
  <!--
    ahhoz, hogy a mix-blend-mode kód működjön a fő containerbe kell írni css-ben nem pedig h1, vagy p-ben....
  -->
  <button type="button" class="btn">gradient+</button>
  <div>

* {
  box-sizing: border-box;
  margin: 0;
}

:root {
  margin: 0;
  padding: 0;
  width: 100%;
  height: 100vh;
  overflow: hidden;
  background-color: rgba(255, 255, 255, 1);
  -webkit-background-color: rgba(255, 255, 255, 1);
  -ms-background-color: rgba(255, 255, 255, 1);
  -moz-background-color: rgba(255, 255, 255, 1);
  font-family: "Source Sans Pro";
}

.container {
  position: absolute;
  transform: translateX(-50%) translateY(-50%);
  top: 50%;
  left: 50%;
  padding: 12px 15px;
  background-image: linear-gradient(-45deg, #0dff0d, #00ffff, #0099ff);
  border-radius: 1000px;
  -webkit-border-radius: 1000px;
  -moz-border-radius: 1000px;
  -ms-border-radius: 1000px;
  background-size: 400% 400%;
  animation: mymove 3s linear infinite;
}

@keyframes mymove {
  0% {
    background-position: 0% 50%;
  }

  50% {
    background-position: 100% 50%;
  }

  100% {
    background-position: 0% 50%;
  }
}

.btn {
  padding: 52px 125px;
  border: none;
  border-radius: 1000px;
  font-weight: bolder;
  font-size: 25px;
  mix-blend-mode: screen;
  letter-spacing: 10px;
  z-index: 10;
}

.btn:active {
  border: none;
  -webkit-border: none;
  -ms-border: none;
  -moz-border: none;
}

//noscript...