Pegasus

In this game, an evil demon called Satan has spread chaos in the world, and
someone has to stop him. This is where you come in. Playing as the hero
Perseus, you have to go to 5 different worlds, each with its own theme, and
kill Satan’s guardians (end of level bosses). A friendly wizard has also given
you a magical flying horse called Pegasus, to help you in your quest.

Each world has 10 levels, and half of them are played flying on Pegasus back,
and the other half walking, without your magical horse. When flying, the game
plays like a Shoot’em up, but when walking, it’s a platform game, and you have
to rely on your sword.

You can buy weapon upgrades and other bonuses, if you collect enough diamonds.
They can be found spread out all over the levels, and fallen enemies drop them
sometimes as well. If your health drops too low, you can also heal yourself by
spending some diamonds.

After every world, you get a password, letting you continue from the same
place the next time you play. That’s fortunate, because this game takes a long
time to complete.