Shadow Era is unity based game and runs great.
Cannon Fodder 3 runs ok, can be tweaked, check it out

Shadow Era

Great card game and totally free, based on unity engine.
Runs great, locked on 30 FPS constant.

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Cannon Fodder 3

Running smooth even with low fps, totally playable.

1280x720 in 8-10 (smooth) FPS
1024x768 in 10-14 FPS
800x600 in 12-16 FPS

I recommend 800x600 for best experience, so just follow next instructions:

Get configuration file from here Cannon Fodder 3 olio Config v1.
Just extract engine.ini and overwrite in main game installation folder
example D:\Program Files\Cannon Fodder 3

NOTE: engine.ini has width and height parameters but it doesn't change them, for custom resolution continue reading.

Change resolution:

start game, goto Settings > Video
change resolution to 1280x720 or 1024x768.

If you want 800x600,
go to C:\Users\YOUR-USER-NAME\Documents\CannonFodder3
and find _profile file and delete it, now extract gpgmgjgp_profile from zip you downloaded earlier (Cannon Fodder 3 olio Config v1) into
C:\Users\YOUR-USER-NAME\Documents\CannonFodder3.

That's all.

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