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print "Using Newton's laws to make the ball bounce realistically"
# updated 2012-10-06 j.m.reneau using loops and subroutines for 0.9.9.x
rem set up initial ball position and speed
x = 20
y = 100
r = 10
yvel = -1.0
xvel = 1.10
yacc = .0098
fastgraphics
do
clg
rem change the downward velocity according to the acceleration
yvel = yvel + yacc
rem calculate new position
y = y + yvel
x = x + xvel
rem check for collisions
if y > 289 then yvel = -0.9 * yvel : y = 289 : xvel = xvel * 0.9
if x > 285 then xvel = -xvel : x = 285
if x < 10 then xvel = -xvel : x = 10
rem draw the ball
call drawBall(x,y,r)
until xvel * xvel < 0.0001
end
subroutine drawBall(x,y,r)
color darkblue
rect 0,0,300,300
color darkgray
circle x, y, r
color gray
circle x, y, r - 2
refresh
end subroutine
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