.grade-btn {
  position: relative;
  overflow: hidden;
}
.grade-btn .bar {
  position: absolute;
  left: 0;
  top: 0;
  bottom: 0;
  width: 0%;
  background: rgba(15, 23, 42, 0.12);
  transform: translateZ(0);
  pointer-events: none;
}
.grade-btn.grading .bar {
  animation: fill linear forwards;
}
@keyframes fill {
  from {
    width: 0%;
  }
  to {
    width: 100%;
  }
}

/* Match highlighting */
.match {
  background: #ecfdf3;
}
.diff {
  background: #fef2f2;
}