SCREEN 12:CLS
SF=0:REM SOUND-1,NO SOUND-0
A=40
B=80
G=0
N=10
NC=0:REM NC-NUMBER OF COLLISIONS
NT=0:REM NT-NUMBER OF COLLISIONS PER TIME UNIT
DIM X(N),Y(N),VX(N),VY(N),OX(N),OY(N),V(N)
PI=4*ATN(1)
RC=1
V=1
DT=.5
KY=3/4
T$=TIME$
T1$=LEFT$(T$,2)
T2$=MID$(T$,4,2)
T3$=RIGHT$(T$,2)
T=VAL(T3$+T2$+T1$+T3$)
RANDOMIZE(T)
WINDOW (-100,-KY*100)-(100,KY*100)
FOR I=1 TO N
FI=2*PI*RND
X(I)=-B+RC+(2*(B-RC))*RND
Y(I)=-A+RC+(2*(A-RC))*RND
VX(I)=V*COS(FI)
VY(I)=V*SIN(FI)
V=SQR(VX(I)^2+VY(I)^2)
OX(I)=X(I)
OY(I)=Y(I)
NEXT I
CLS
'?"IMPACT1"
'?"PARTICLES NUMER=";N
'?"COLLIDION RADIUS=";RC
'?"TIME QUANTUM=";DT
'?"INITIAL VELOSITY=";V
LINE (-B,A)-(B,-A),1,B
FOR I=1 TO N
CIRCLE (X(I),Y(I)),RC,2
OX(I)=X(I):OY(I)=Y(I)
NEXT I
?"2D->1D gas"
?"<Esc>-to quit"
MOVING:
 FOR I=1 TO N
 IF INKEY$=CHR$(27) THEN STOP
 GOSUB IMPACT
 GOSUB WALLS
 X(I)=X(I)+VX(I)*DT
 'VY(I)=VY(I)-G*DT
 Y(I)=Y(I)+VY(I)*DT
 CIRCLE(OX(I),OY(I)),RC,0
 'line (-b,a)-(b,-a),0,b
 LINE (-B,A)-(B,-A),3,B
 CIRCLE(X(I),Y(I)),RC,2
 OX(I)=X(I):OY(I)=Y(I)
 NEXT I
 if a>=rc then line (-b,a)-(b,-a),0,b:a=a-.0002*a: line(-b,a)-(b,-a),3,b
GOTO MOVING
WALLS:
 IF (X(I)<(-B+1+RC) AND VX(I)<0) OR (X(I)>(B-1-RC) AND VX(I)>0) THEN VX(I)=-VX(I)
 IF (Y(I)<(-A+1+RC) AND VY(I)<0) OR (Y(I)>(A-1-RC) AND VY(I)>0) THEN VY(I)=-VY(I)
RETURN
IMPACT:
 FOR J=1 TO N
 AX=X(J)-X(I):AY=Y(J)-Y(I)
 VRX=VX(I)-VX(J):VRY=VY(I)-VY(J)
 VR=SQR(VRX^2+VRY^2)
 SCAL=VRX*AX+VRY*AY
 DIS=SQR(AX^2+AY^2)
 IF DIS <= 2*RC AND I<>J AND SCAL>0 THEN GOSUB IMPACT1
 NEXT J
RETURN
IMPACT1:
 V(I)=SQR(VX(I)^2+VY(I)^2)
 V(J)=SQR(VX(J)^2+VY(J)^2)
 PX=VX(I)+VX(J):PY=VY(I)+VY(J)
 SOUND 10000,.0001*SF
 SCAL1=VX(I)*AX+VY(I)*AY
 SCAL2=VX(J)*AX+VY(J)*AY
 VNI=(SCAL1/DIS)
 VNJ=(SCAL2/DIS)
 VTI=SQR(V(I)^2-VNI^2)
 VTJ=SQR(V(J)^2-VNJ^2)
 VNXI=VNI*AX/DIS
 VNYI=VNI*AY/DIS
 VNXJ=VNJ*AX/DIS
 VNYJ=VNJ*AY/DIS
 VTXI=VX(I)-VNXI
 VTYI=VY(I)-VNYI
 VTXJ=VX(J)-VNXJ
 VTYJ=VY(J)-VNYJ
 VX(I)=VTXI+VNXJ
 VY(I)=VTYI+VNYJ
 REM VX(J)=VTXJ+VNXI
 REM VY(J)=VTYJ+VNYI
 VX(J)=PX-VX(I)
 VY(J)=PY-VY(I)
 V(I)=SQR(VX(I)^2+VY(I)^2)
 V(J)=SQR(VX(J)^2+VY(J)^2)
 NC=NC+1
RETURN