At the top of the sky gradient color list, where you would put a direction for the gradient; add circle closest-corner at 15% 15%,. This will move the start of the gradient to 15% from the top and left. It will make it end at the closest-corner and it will maintain a circle shape. These are some keywords built into gradients to describe how it behaves.
code does not pass
.sky {direction: circle closest-corner at 15% 15%;
background: radial-gradient(
#ffcf33,
#ffcf33 20%,
#ffff66 21%,
#bbeeff 100%
);
}```