REM ==comet3xx Basic Source File =====
REM
REM
REM console 1
SCREEN 88, 0
REM
REM ==inputation for  some parameters=====
pxs0# = 1
pys0# = 0

REM =======================================
REM firstspeed-vector cerestron's

REM speedtheta#
INPUT "vector speed degree -180 to +180"; speedtheta#
REM speedbigth#
INPUT "speed-bigth 0 to 10 Unit is EarthSpeed"; speedbigth#
REM V0(vx0,vy0)
speedearth# = 2 * 3.141592 / 365.251

vx0# = speedearth# * speedbigth# * COS(2 * 3.141592 * (speedtheta# + 90) / 360)
vy0# = speedearth# * speedbigth# * SIN(2 * 3.141592 * (speedtheta# + 90) / 360)

REM =========================================
REM time parameters.
REM input deltatimedays
REM deltatimedays first:1/4 days of earth.
deltatimedays = 1 / 4
PRINT deltatimedays
INPUT "HOWLONG by years"; howlong
howlong = howlong * 365.251
REM   
PRINT howlong  '''''''''''                   
REM ==Constant parameter========
REM 62:the local number in this machines.envilonment.
gconst = 5.2 * 10 ^ (-8)
sungrv = 3.3 * 10 ^ 5 * gconst * speedearth#
REM ==graphics sclae========
howauperhalfxmoni = 5

REM ===========================================================
REM =================== main core =============================
REM ===========================================================
REM counterstep is 0 then next.
REM s:sigma mean.
pxs# = pxs0#: pys# = pys0#
vxs# = vx0#: vys# = vy0#
REM axs# = 0#: ays# = 0#
REM rem
REM
REM ==============
counter = 0
CIRCLE (320, 200), (320 / howauperhalfxmoni)
stepagain:
REM ==important core!!========E
d# = pxs# ^ 2 + pys# ^ 2

ax# = -sungrv * pxs# / (d# ^ (3 / 2))
ay# = -sungrv * pys# / (d# ^ (3 / 2))
REM =====
REM =====
axs# = ax#
ays# = ay#
vxs# = vxs# + axs# * deltatimedays
vys# = vys# + ays# * deltatimedays
pxs# = pxs# + vxs# * deltatimedays
pys# = pys# + vys# * deltatimedays

REM ========== main core's end ================================
REM ========== Grafic drawing =================================
REM grafic for EGA:640*400
xmoni = 640: ymoni = 400
ktemp = (640 / 2) * (1 / howauperhalfxmoni)     'left -5 AU, right +5A.
dotx = xmoni / 2 + ktemp * pxs#
doty = ymoni / 2 - ktemp * pys#
REM PRINT pxs#; pys#
REM PRINT dotx; doty
PSET (dotx, doty), 2

REM
IF howlong < counter THEN INPUT "HIT ANY KEY"; end$: END
counter = counter + deltatimedays
GOTO stepagain
REM ===========================================================