How do I know what size to make my layout/window?

After reading Fronne 's tutorial on mulitple screen sizes, I think that I understand that the ratio of my game's display is what is important. I want to make a side scrolling game that looks like a city block (several unique buildings on the block that my player will interact with). My layout will be very wide so that my player can walk from end to end of the street. However, I can set my window to the 16:9 ratio, right? As long as the math of the window follows this ratio I am good for displaying on different devices? I am TOTALLY new to this (an artist, not a programmer...trying to become a one stop shop for gaming content) so I am trying to wrap my head around this. Please, help!

BTW, the tutorial is found under the beginners section with the title "Multiple screen sizing for all mobile devices". I am too new to post a link.

Hi growstudios and welcome to the forums. This is a topic that has many approaches so it depends on which you prefer. The approach I like to use is this:

If you are only targeting 16:9 ratio, it is simple, just select the screen resolution that you prefer and work from there.

If you are setting up for multiple aspect ratios, I usually select 2 or 3 of the most used ratios, create a bounding box with those ratios, and set them in the middle of the layout. All boxes are transparent in the middle, they just have edges so I can see them. From there, I design my game so that

a) All the vital parts can be seen from all the different ratio boxes. (the intersection of all ratio box)

b) No unwanted objects can be viewed from any of the ratio boxes. (every part of all the ratio box)

For example, a vertically longer aspect ration will show more of the floor than a shorter one. So it is important to make sure that the graphics don't cut off suddenly or display things that are not supposed to be seen.