Choosing the right window size

In brief, computer game developers have two options available to them, with regards to the game window. Should it be Fullscreen? Or Should it be Windowed? However this all depends on what type of game it is. Choosing what size the window is could be done at any stage in development. But if you are wise you will decide at the beginnning, when you conduct all of your planning so as you can shape and model the game around that window size.

Full Screen
This is a very popular choice for story driven games, as it is visually pleasing and helps to immerse players into the game. But before going for full screen, look at your resources. Will the sprites that you have look good in full screen? Or will they take from the experience by looking poorly stretched?

Windowed
If you want to go for a windowed game, the next step to getting the window right is in getting the window size right. Look through the following to see which one suits you.

Small Windows
Usually small windows are only used in puzzle games, as they can be difficult to see in RPGs or other game types. My research shows that they tend to create relaxed feelings, but a lack of variety on screen can easily bore players.

Medium Windows
This is always a safe choice, the default room size (640x480) is fine for a variety of games, but if you do want to break away from those defaults and create something totally new, I'd move away from this. Variety and originality in the game itself is highlighted, but steer clear if your game has been done (in any way) before.

Large Windows
If you are going to go with a large sized window, you should consider just going into full screen. But none-the-less large windows definitely immerse the player, and get them to realize they are playing a good game, but if your game isn't exactly that, if it gets boring after a while, steer clear of this size.

Testing
When testing to see did you get the window size right, try out these phases.

Try it yourself
Firstly, it is most important that the game feels right to you, you're the developer, and you should know what it is supposed to create, does it create that?

See how others feel
Write down what feelings you want to conjure up with the window size. Do you want them to feel afraid, totally immersed in a haunted house? Or in another situation, highlighting to the player that they are relaxed?

Ask some friends or family to play the game, for a set amount of time each.

Ask the testers to participate in a brief survey, asking them how they felt during gameplay.

Compare those results to how you wanted them to feel, then if necessary, tweak the window size until you get the desired results. It's all about trial and error.

If you are repeating testing, try to use different testers if possible. And remember, this testing doesn't have to be confined to your family and friends, you could ask people online too.

Final Word
I hope that this tutorial has helped you to hone your skills in choosing the correct window size, good luck!