I found another Mandelbrot/Julia generator for the NDS (and not this one). And tried to implement it myself. It works like a charm. I use 32 bit fp (6.36) or 64 bit (6.58). It can zoom in 26 times, each time a factor 4 (So a total of 2^52). Afterwards switching to float or double is not necessary (and doesn’t help, since fp is more accurate in this case. [Not sure what you mean by 175x].

Will post my contribution after adding some more twists. The point is that I tried periodicity checking. It requires some finetuning WHEN to check for periodicity (for instance only if you know the last point was part of the basin of attraction) and HOW OFTEN to check for periodicity once you’ve decided to use it (for a particular starting “x,y”), because if the list of saved values increases, say length n, the order of the checking can be O(n^2). Maybe sorting the values you intend to keep can help, but than the sorting part takes extra time. [I didn't find a speed increase, quite the opposite]. But than again, the storing and checking part can still be optimised].

This is one of my favorite homebrew apps, but it doesn’t save. Oh noes!