Wow. Just wow. This was absurdly hard. For those trying to achieve the last medal, you can't do it without the youtube walkthrough. Well.... you can but will be really painful.
AS a whole game, it is too hard, it gave me a bad time. Only "fun" on normal and easy modes. Other than that, for a 10 year old flash, it's good. Only flaws are the respawning bats (a flawed mechanic that adds a lot of difficulty that isn't needed, as killing them can harm the player as they reappear without notice and sometimes at a different height.
Other minus is the ending - not the rickroll part, but the protagonist shown as a greedy soab - stealing the recipe book. man, he's a hard working individual, he would NOT do that, even more after all he just DID! That was a tragic break of character, and a really bad move.
My "method" was a bit different but a sure-fire way to complete the whole game without dying.
1- Open the game on multiple tabs, as much as you can without lagging.
2- Start a game in every tab.
3- Complete the 1st level on EACH tab (preferably as the walkthrough dictates)
4- Keep the pace (1 level each time, each tab).
5- When you die at a certain level, or get hit at an easy level, close that tab and go to the next trying to do differently - Short memory is reliable, if you restarted the game, you could forgotten your mistake.
6- Keep on until you finish. In the end, your game will be much longer, but you'll have a greater chance at achieving one of the hardest medals ever on NG.
2 valuable tips
Level 14 is easier if you use the KEY as a "step" to avoid barrels, climbing on it when they come down.
Level 15 (final battle) is much easier if you make a small ladder of boxes on one of the upper platforms sides, in a way that falling boxes pile up on them. They'll keep piling up and you can get high enough to throw boxes on robots head but be careful because enemies can drop from it too.