Not great
The Ishihara plates are pixelated, which seems a bit lazy to me. There doesn’t appear to be any way to vary the snellen chart to get different letters (there are so many of the same letter on the same line e.g. multiple O or D or C on the same line it’s unrealistic), you can’t adjust for your personal phone screen size so I don’t think it can be accurate depending on the phone you’re using. There are no markers on the side of the chart saying what is 20/20 or 6/6 vision so how is this meant to be helpful at all?