not to many people have this game....but it's really funny
When you grabbed the final heart on each level, it activated the enemies. In other words, inanimate enemies were brought to life and would chase you. You had to plan your movements so as not to get caught by the now-active enemies. That doesn't mean the game was easy before the enemies were activated... as many levels had some enemies which were active before you grab the final heart. For example, there was an orange creature -- I believe this was the Medusa, if I'm not mistaken -- which rendered you frozen if you stood in its line of sight. Get into the Medusa's line of sight, and you would be frozen and shot to death with a flying sword/knife. You had to plan your movements and plan which blocks to move around, when, and where to move them around in order to block the line of sight of such enemies.