@property --percentage {
  initial-value: 0%;
  inherits: false;
  syntax: "<percentage>";
}

.chart {
  background: conic-gradient(red var(--percentage), white 0);
  border-radius: 50%;
  width: 80vmin;
  height: 80vmin;
  animation: timer 4s infinite linear;
}

@keyframes timer {
  to {
    --percentage: 100%;
  }
}

body {
  height: 100vh;
  margin: 0;
  display: grid;
  place-items: center;
  box-sizing: border-box;
  padding: 2rem;
}