z → z2 + c  explorer
%/frame
c = 0 + 0i
Mandelbrot  c = pixel, z0=0
Julia  z0=pixel, c fixed

Mouse controls

Left-dragzoom to rectangle
Right-clickzoom out ×2 at cursor
Ctrl + Leftset Julia c (Mandelbrot view; drag to scrub)
Shift + Left (hold)continuous zoom in at cursor
Shift + Right (hold)continuous zoom out at cursor