I'm writing this tutorial because some members are not familiar with that, since they used to work on some programs like The Game Factory, for example.
If you look closely, every sonic level is made of 16x16 tiles. 16x16 tiles are graphics blocs of 16 pixels dimensions.
All the levels parts that aren't objects are made with those tiles. They can be animated, but only with a rotating palette.
I'll take example on Aquatic Ruins Zone to illustrate my point. Here are some 16x16 tiles of this zone :
Due to the Genesis limitations, the number of those tiles are limited.
As we're using E02 engine, we need our levels to be structured like that.
Here is, for example, my tileset from Cosmic City zone :
I recommand you to work like Resel and I do. We're using a bitmap grid :
This is mainly the work of the sprites artists that are making levels on paint.
Keep in mind that backgrounds are made the same way, but with 8x8 pixels blocs. If you draw some, think of the multiple scrollings : each 8 pixels line can move at a different speed.
From the 16x16 tiles, are made a lot of 128x128 tiles. Here are some examples :
This part is very important, because even if we have a small amount of 16x16 tiles, we can and we have to make a lot of those 128x128 pixels blocs.
This part is not the main work of a sprite artist, as everyone can make it. You just have to put together 16x16 tiles. If you have immagination, you can make a lot of good 128x128 tiles.
Here is a link to Gba Graphics, a tool made by my friend Brunni, and that will help you a lot doing that job :
A tutorial will be released soon for this program.
I recommand you to look at the 128x128 tiles of Sonic levels with SonED (like Ice Cap if you're making a snow level). It helps a lot to see what kind of blocs are used/needed.
Now, here is the level designers work. Once we have all the 128x128 blocs we need, we can make the map, but ONLY with those blocs.
If you look at a sonic level map, you can see that easily :
You can see that a sonic map is kinda repetitive, but that's not very a problem, since you don't notice that when playing.
Every background part that moves or that you can interact with is an object. It isnt restricted by the 16x16 tiles, and should be drawn independently.
For example, moving plateformes, spikes, lamp post, but blocs that you can break, too.