I have this weird problem: when I create a circle (no antialiasing, mechanical pencil used) while the image is in 100% mode, the circle looks as I'd expect. But if I zoom in to, say, 500% and do the same, the resulting circle is distorted and looks like a potato. I tried switching on the grid and setting it to snap and 1x1, but that didn't help.
Also, is there a simple tool that would just draw using a single pixel? Pixelling using all those advanced tools gets a bit rough at times

Thanks,
Pavel