My father beat this game when i was a kid. Took him while, it has password based saves.
The hearts are the currency in the game that are used to buy health or hammers from merchants. It's a climb to the top style scroller. If you fall of the screen your dead it doesn't go back down.
The flying eyes do a figure eight on the screen and essentially stay just above your jumping height for abit, not too much of a challenge just annoying.
The grim reaper looking guys are rather annoying they take a few shots to kill and if they see you they summon 4 small grim reapers which are like the eyes but home in on you.
The statues on this screen are angels that have been turned to stone by medusa. You need to get hammers to free them. before you can even fight the boss of the first level.
I haven't had the time to sit down and go through the game in its entirety at this point but it can be challenging even at this point.