Dear Mike (and/or anyone else if interested), I like the math approach in your F_20150409_1343 fractal formula. I experimented a lot with multiple variable systems, mainly with one I found somewhere included with an old 80's fractal program. This formula might be included in other programs as well but my search for an other name, original purpose (if there is any) or creator resulted in nothing. Here I post this original formula (AB-) with a bailout value way larger than the original, that is the only main change I've made to it. You'll have to zoom out a bit if you load the formula. An other formula I post is from my experimentation branching from this one, with two parameter files (DLs08-0101 and DLs08-0102). If anyone knows more about systems acting similarly, please point me to the right place. Have a nice day, B.D. ---formula-start------------------------------------------- AB- { a = b = pixel bailout = 1E+100 : a = sqr(a /b) +a b = sqr(b /a) +b |a|+|b| <= bailout } ---formula-end--------------------------------------------- ---parameters-start---------------------------------------- DLs08-0101 { reset=2099 type=formula formulaname=DLs08-01 center-mag=-3.88284/0.696062/0.2224559/1 params=-0.0032/1.0368/0.992/-0.006/-1/0/0.0025/0.0046875/11/0 float=y maxiter=300 inside=0 periodicity=0 colors=000<24>00n00p00r<2>00x00z00z<24>nnzppzrrz<2>xxzzzzzzz<24>CCzAAz88\ z<2>22z00z00z<24>00C00A008<2>002000000<24>0an0cp0dr<2>0ix0jz0jz<24>nwzpx\ zrxz<2>xzzzzzzzz<24>CnzAmz8mz<2>2kz0jz0jz<30>000 } DLs08-0102 { reset=2099 type=formula formulaname=DLs08-01 center-mag=-2.24553/1.05099/0.2127981/1 params=1.0404348100300811/-0.095741680046563471/1.12/-0.12/1/0/0/-0.01875/8/0 float=y maxiter=500 inside=0 periodicity=0 colors=00000C<18>00n00p00r<2>00x00z00z<24>nnzppzrrz<2>xxzzzzzzz<24>CCzAA\ z88z<2>22z00z00z<24>00C00A008<2>002000000<24>P0nQ0pR0r<2>U0xW0zW0z<24>tn\ zupzvrz<2>yxzzzzzzz<24>aCz`Az_8z<2>X2zW0zW0z<24>60C50A408<3>000<4>00A } frm:DLs08-01 { a = pixel b = pixel +(2.5 +flip(-3)) c = pixel +5 n = m = n_t = 1 n_iter = 0 n_level = real(p5) bailout = 1E+100 : n_iter = n_iter +1 IF (n_iter == n_level) n_t = n n = n +m m = n_t n_iter = 0 ENDIF a = a +(n *p4), b = b +(n *p4) a = sqr(a /b /c) +a *p1 b = sqr(b /a /c) +b *p2 c = sqr(c /a /b) +c *p3 |a|+|b|+|c| <= bailout } ---parameters-end------------------------------------------