Screen 12
K = 15
FOR X = 0 TO 3: FOR Y = 0 TO 3
 
AX = 80 + X * 120: AY = 120 * Y: BX = 200 + 120 * X: BY = AY
CX = BX: CY = 120 * (Y + 1) - 1: DX = AX: DY = CY

FOR J = 1 TO 24

LINE (AX, AY)-(BX, BY), 10
LINE (BX, BY)-(CX, CY), 12
LINE (CX, CY)-(DX, DY), 9
LINE (DX, DY)-(AX, AY), 13

AX = AX + (DX - AX) / K: AY = AY + (DY - AY) / K
BX = BX + (AX - BX) / K: BY = BY + (AY - BY) / K
CX = CX + (BX - CX) / K: CY = CY + (BY - CY) / K
DX = DX + (CX - DX) / K: DY = DY + (CY - DY) / K

NEXT J

NEXT Y: NEXT X
SLEEP 555