From: Regis d'Aubarede <lists@...>
Date: 2013-06-07T03:51:09+09:00
Subject: Re: My car is "falling" off the screen green shoes

and then, a little physics


==========================================================
require 'green_shoes'

def inside(a,m,b) m<a ? a : (m> b ? b : m) end
def inside?(a,m,b)  inside(a,m,b)==m end

Shoes.app :width => 600,:height=> 100 do
  info= para ""
  @carim = image "car.png" #!!!!!

  speed=10
  acceleration=0.0
  pos=300

  h={"Left" => -0.3 , "Right" => +0.4 }

  keypress do |k|
    acceleration = inside(-10, (acceleration+(h[k] || 0)) ,+10)
  end

  animate do
    speed+=acceleration
    speed*=0.97
    acceleration=0
    speed *= -1 unless inside?(0,pos+speed,width-@carim.width)
    pos=pos+speed
    speed=inside(-10,speed,+10)

    @carim.move pos, 100-@carim.height
    info.replace "  Speed=%5.2f " %[speed]
  end
end
==========================================================

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