Scanlines are supported already, however a USB joystick is currently not supported, you have to use an Atari/Commodore-style jostick.
Currently only the 16K-expanded VIC is supported, that means that you can only run games that would run on a 16K-expanded VIC. [EDIT: since yesterday there is a new version of the core, and now you can switch between unexpanded VIC, 3K expansion and 16K expansion. There is no reset option in the menu yet, so you have to type SYS 64802 after changing the memory options to reset your VIC.] [EDIT #2: instead you can simply press the MIST's right button to reset the VIC.]
The core seems to be running very well, almost all 16 KB games that I tried ran perfectly.
However, there is a faint diagonal line across the bottom part of the picture - don't know what this is, and I haven't tried it yet on another display than my 17" CRT monitor.
For those who still don't know about this beautiful little toy called MIST: here you can find some basic information about it, here is the main repository for cores and firmware (however for some reason the latest Atari 800 and 5200 cores are not not available there, as well as the great PC Engine core), and here you can order it.
Best regards and merry Christmas to those of you who celebrate Christmas!
Robert
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