From Uwe Geiken:

A little play with regular polygons :-)
10 INK 5: PAPER 0: BORDER 0: CLS
20 LET cx=128: LET cy=87: LET r=12
30 FOR n=3 TO 27
40 CIRCLE cx,cy,r
50 LET r=r/COS (PI/n)
60 PLOT cx,cy+r
70 LET s=2*PI/n
80 FOR p=0 TO 2*PI+s/4 STEP s
90 DRAW cx+r*SIN p-PEEK 23677,cy+r*COS
p-PEEK 23678
100 NEXT p
110 NEXT n`