Do you remember macpaint? I hadn't, but kicks condor brought it up.
It's nostalgic - I remember it being somehow intensely important to choose which pattern was my favorite.
Anyway, this is just bananapaint, an ipad app replacement that doesn't let you make a 1px line and seems to have coarsened the pattern fills... but the pencil support and photo imports make it good enough to put up with that.
More nostalgic still would be Kid Pix, though less credible as a tool for Actual Art. Thinking back on my childhood I feel so lucky to have been able to play with computers as things for creativity and expression.