I have noted the bugs and will try to solve them: especially the second boat and the stairs around Apollo, adjust the height of the jump.
For the checkpoints, I come from the days of Super Mario on Game Boy: you had 3 lives to finish everything. If you lost them: back to square one. Besides, you only have one game, because it was expensive and you had to convince your parents to go and buy it in a store far from you. So you start over and over again until you are successful. The best day of your life is when a friend has the same game and you play side by side. How you laugh when he has to start all over again!
Ok, things have changed and so have the games.
Have you found the power of fountains? I don't know if it's intuitive enough.