I don't want to give a spoiler away for the coin, but the arrow points exactly to the coin. But, the path to get there is not always in a straight line. There are now special rooms, entrances, or anything to get to where the coin is, you just have to explore the areas where the arrow points.
Funny thing I have noticed...I have been playing all the retro games to get my levels as close as possible down to the last pixel. Same thing with how the cameras follow etc. And you would be amazed how many bugs I have found in the retro games. I also see where they took short cuts, and ran into a lot of the problems that I have building the levels. I can see now why they did a lot of the things they did in certain games. One of the biggest mistakes I have seen, and it is in a lot of them, is that they did not set the camera correctly going from one room to another. So you can see the camera shift to try and compensate, or I have even seen graphical glitches because of these transitions. Man...I may have messed up video game playing for myself now. It doesn't matter what game I play now, I can't help but diagnose how they built the level, or why things are as they are.
Actually, I haven't really played any games for fun in a year now. I play them to research for my game.
This last week, I have gotten rid of a lot of the areas I don't like. Not whole levels, but things that are unnecessary or boring. I tamed the difficulty level down in some areas, and increased it in others where needed. I am playing every level a million times until every part is perfect. In fact most of the time I am on the computer, I have Desmume open in one window, and I am editing my game in another. Mouse in one hand, USB controller in the other.