Spent about 1 1/2 hours and beat 3 levels (dark and light versions) as well as 2 warp zones. I have found that while I have very little problem repeating normal levels tens or even hundreds of times, I get incredibly frustrated in a warp zone after having to restart just 5 or 6 times. I think that the fact that every time you get a game over in a warp zone you get kicked back to map, then you have to see and hear the "warp zone" video, only a few seconds long, but unskippable, then you are taken to the title screen, and finally you are allowed to retry the three stages. The whole process only takes 5-10 seconds each time, but that delay, along with the repetitive visuals and sounds really get to you after any large number of tries. So, I waste 10 seconds and possibly have to do other stages over again to retry what I failed instead of being able to retry the same level immediately, like in the normal stages. I really do think that this small difference in wait time makes a huge difference in the level of frustration incurred by the player, because despite being significantly easier than the main game (retro levels probably only take between 15 and 30 lives to beat on average, vs. 30-100 for the other levels) it manages to frustrate me much more.