html,
body {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

:root {
  --progressbar-width: 380px;
  --progressbar-height: 40px;
  --progressbar-bg: lightgrey;
  --start: red;
  --middle: blue;
  --finish: green;
}

body {
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
}

/* start styling */
.progress-bar {
  background-color: var(--progressbar-bg);
  width: var(--progressbar-width);
  height: var(--progressbar-height);
  border-radius: var(--progressbar-height);
}

.progress-status {
  width: 10%;
  background-color: var(--start);
  animation: grow linear 6s infinite;
}

@keyframes grow {
  50% {
    background-color: var(--middle);
    width: 50%;
  }
  100% {
    background-color: var(--finish);
    width: 100%;
  }
}