By far my favorite Metroidvania *ever*. Its deceptively simple storyline manages to be incredibly compelling (when I got the first bad ending, I was absolutely shocked by the revelation). Great and responsive controls, a good amount of variety in the regions, and a perfect length - took me about an hour the first time I played it, but I was able to complete the other endings in about 20 minutes each using the skills I'd built up from the first run-through.