There are many things missing and wrong here. First off, on level three when the bridge opens up, the lava trolls have been cut out, not to mention that touching the lava results in instant death. The law of gravity has been repealed; you push the button a few times and you shoot straight up, and the eggs never touch the platforms -- they just float until something happens. The graphics are poorly drawn, the sprites of your character and the enemies look the same (except for different colors) and don't get me started about the pterodactyl.
Joust is a poor conversion of a great game. Some players may overlook its weaknesses and find some enjoyment, but I'm not making any such promises since there are better ports out there.