Not Bad, But Can Use Improvement
I will make the make longer/add preloader comments short per your request, but do realize they can make or break a flash. I do realize that you want to improve the basic concept before you make it longer and add the preloader, though. Here's a few tips:
Nice background, but hard to see - For instance, on level two, I couldn't see the thin black line that forces you to go into the "windmill" area. Making said line white will contrast it against the motherboard. Barring that, maybe making the background lighter would help.
Prevent right-click winning - Granted, I am not familiar with the method required to do so, but I'm sure a quick tutorial in AS will teach you how. Just a thought if you want people to work for victory, rather than cheat. ;-)
Make it so you don't have to click to get to the next level - While it's good to click on "Start" to prep you for the level, it's not necessary for the end. I'd just switch the button code to be triggered when mouseovered instead of clicked.
Keep it up - You have a lot of potential here, and I'd like to see you keep working on it. Just make sure, once you get the game the way you want it, to add that preloader! :-)