REM PROGRAM KEPLER STARTED 27 JUNE 1996
REM THIS PROGRAM SHOWS THE PLANETS AS THEY ORBIT THE SUN
REM FROM THE PERSPECTIVE OF A VIEWER AT 2 RE FROM SUN
REM ONLY PROBLEM IS BLINKING
SCREEN 12: WINDOW (-2, -2)-(2, 2)
REM PLANET'S DISTANCES AND RADII IN RELATIVE UNITS
NP = 4: REM EXCLUDES JUPITER
D(1) = .39: D(2) = .72: D(3) = 1: D(4) = 1.52: D(5) = 5.2
R(1) = .4: R(2) = .99: R(3) = 1: R(4) = .54: R(5) = 3
HUE(1) = 7: HUE(2) = 15: HUE(3) = 3: HUE(4) = 12: HUE(5) = 6
RSUN = .1: DOBS = 2
DTHTA = -.03: PI = 3.141593
YSCL = .5: PLNSCL = .02
CIRCLE (0, 0), RSUN, 14
PAINT (0, 0), 14
FOR I = 1 TO 5
TH(I) = 0
R(I) = PLNSCL * R(I)
X(I) = D(I) * SIN(TH(I))
Y(I) = YSCL * D(I) * COS(TH(I))
DTH(I) = DTHTA * D(I) ^ (-1.5)
NEXT I
FOR J = 1 TO 1000
FOR I = 1 TO NP
TH(I) = TH(I) + DTH(I)
X(I) = D(I) * SIN(TH(I))
Y(I) = YSCL * D(I) * COS(TH(I))
MAG(I) = 3 / (DOBS + Y(I) / YSCL)
CIRCLE (X(I), Y(I)), R(I) * MAG(I), HUE(I)
PAINT (X(I), Y(I)), HUE(I)
NEXT I
CIRCLE (0, 0), RSUN, 14
PAINT (0, 0), 14
REM WHILE INKEY$ = "": WEND
FOR KK = 1 TO 2000
NEXT KK
FOR I = 1 TO NP
CIRCLE (X(I), Y(I)), R(I) * MAG(I), 0
PAINT (X(I), Y(I)), 0
NEXT I
NEXT J