[MENTION=30815]Progject[/MENTION]
There is no need to make your own level editor today, the only reason why people made it was because the code reuse issue in the past but with fusion 2.5+ there is no need for that anymore. The workflow by using fusion out of the box is also way more convenient than spending all your time developing your own frame/world editor when fusion already have one!
If you wanna make big levels its no problem, fusion is one of this engines that have very smooth performance out of the box, even on mobile, if you use it correctly. The rule is basically, use as often as you can quick backdrop or backdrop objects and actives only for things you really need them, like player, enemy, moving objects etc. NEVER use actives for building levels, NEVER. Actives are very heavy on performance, as said above already you will get lot of stuttering motion and performance issues, especially on mobile, by using to much of them.
Look in the example.mfa, where i make a big frame (16000x2000) and plaster it with quick backdrops, as you can see the performance is very smooth, even on lower mobile phones.
You could also use an external editor for tileset level creation like ( Please login to see this link. ) and export your build level as a single png's (but i would not go over 2k for a single image), load it in fusion and set up you collision with transparent backdrops, this will also give you a very good performance. Its always better to use big prebuild world images instead of building your levels with lot of seperate tiles in fusion.
But as said above already it only really matters if you develop for mobile, tablets and desktop PC, for desktop PC alone you have mostly no performance issue, only if your game is really big with lot of stuff going on at the same time.
Conclusion: Fusion is very smooth and top performing with moderate use of big textures, plastering the frame with hundrets of small actives on the other hand is a big NO NO.