The following GFA BASIC for Atari ST code was translated in p5.js :
Cls
Graphmode 3
A=Xrsl%/2
B=Yrsl%/2
'
For I=1 To 11
R=Yrsl%*0.7
For W=Pi/4 To 3.6 Step 0.05
X=R*Cos(W)
Y=R*Sin(W)
Line A+X,B-Y,A-Y,B-X
Line A-Y,B-X,A-X,B+X
Line A-X,B+Y,A+X,B-Y
Line A-X,B+Y,A+Y,B+X
Line A+X,B+X,A+X,B-Y
R=R*0.94
Next W
'
R=R/0.94
For W=3.6 To Pi/4 Step -0.05
X=R*Cos(W)
Y=R*Sin(W)
Line A+X,B-Y,A-Y,B-X
Line A-Y,B-X,A-X,B+X
Line A-X,B+Y,A+X,B-Y
Line A-X,B+Y,A+Y,B+X
Line A+X,B+X,A+X,B-Y
R=R/0.94
Next W
Next I
'
Pause 100