{
mutable animationRunning = !mutable animationRunning;
if (startAnimation) {
let start = 0.02;
let end = 4.0;
let step = 0.005;
let delay = 1;
for (let value = start; value <= end; value += step) {
if (!mutable animationRunning) break;
yield Promises.tick(delay);
mutable currentValue = value;
}
}
}