how do I launch the game in a window?
There a section dedicated to that inside the included readme file. Try some of those solutions to see if that fixes your problem.
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Fullscreen:
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*Your monitor needs to support at least a resolution of 1280x960 to see the whole screen!
*Monitors with vertical resolution less then 960 will not be able to display the game properly!
Starting the game in full screen mode might cause issues.
Don't start the game in full screen mode but use F5 to make it full screen.
Press F1 and uncheck start full screen if it's checked...
OR
Edit the game.ini and make sure Fullscreen=0. (Restart game after.)
Open the game.ini with a texteditor and change Fullscreen=1 to Fullscreen=0
OR
If the game is active try ALT+ enter to exit/enter full screen mode.
Use F5\F6 and make it windowed
Because RPG maker used 4:3 resolution some black bars will be present when using widescreen A.k 19:6 etc..
There are a lot of different posts regarding the "screen being cut off" when launching this game in either full screen or windowed.It seem these problems arise in particular with people who are using a laptop. There is a consensus that updating video drivers can help.
It seems unknown to many that RGSS, in all its versions, shares the configuration from the F1 menu for all games. So, for example, all games made using RGSS3 share the same F1 config, if you change it for one, you change it for every other game.
To change that, you can use regedit.(CAREFULLY!!! Careless use of regedit can screw up your entire PC!)
Look for:
HKEY_CURRENT_USER -> Software -> Enterbrain -> RGSS3 (or the version your game uses).
Right click on LaunchInFullScreen and select Edit (First option), set the value to