This hack is a decent one. The design isn't top-noch, but it's not too awful either. This one involves around exploration, so there are different paths to take and hidden secret sublevels with coins as reward. Sometimes it felt like the author rushed in making his level (mostly the ones at the end of the demo), while others felt a bit too empty. Yet, it's not totally bad.
Aesthetics are okay. The author used the basic vanilla gfx. Sometimes level lacked decorations and felt way too empty. Some of the palettes also look wrong, like the cave background.
Overall, 2/5. Not extremly fun, but it's in the borderline of decency.