Ended the citadel challenges Trophy in A Boy and His Blob

You may have noticed that every time you collect three treasure chests in any level, a new item will appear in your hideout. These are the challenge levels. Challenge levels are very short, but the downside is that there are no checkpoints – dying means starting from the beginning. Usually these will not pose a problem, but some will make you frustrated. Remember: these aren't timed, so go as slowly as you'd like to avoid making mistakes.

Note that there are only eight challenge stages in the citadel world, as there are only eight levels in this world.

PurPleeHaze has made a YouTube walkthrough for these levels; find it HERE.