I've made this program for myself, but I think somebody else can find this program useful.
Changing map settings such as AR/CS/OD isn't so hard to do manually, but it was taking too much time for me (I'm too lazy) when I wanted to practice little circles or low AR. Also there is an useless function to replace sliders to circles
How to use it:
1) Run it, select songs folder, set a hotkey
2) Start the diff you want to change
3) Make sure that you're playing in a windowed mode, then look at the title, when it has the song name - press a hotkey
4) Change anything you want there, press the button
5) Play a new diff.
New diff will be smth like [<old diff> CS7 AR10 OD10 NS] (NS = nosliders)
Some important thing: you must have your default keyboard layout language as english, otherwise the program might not work (for example if it's russian keyboard layout). I can't to anything with that, the program does set your keyboard layout to english at starting it, but my friend (with win8) still has the error appearing, so idk.
Setting default kb layout to english:
http://u.to/vRvGBQ (win8 - select english there)
http://u.to/gR3GBQ (win7 and others)
There are some bugs, sometimes it doesn't work at all, sometimes it makes an unplayable map, whatever. I don't care.