basicSim update

emulationSpeed=3000
frameskip=100
G=6.67384*10^-11 --N(m/kg)^2
obj_mt={}

obj_mt.compare=function(self,obj)
    if self.pos and obj.pos then
        return ((obj.pos[1]-self.pos[1])^2+(obj.pos[2]-self.pos[2])^2)^0.5,math.atan2(obj.pos[2]-self.pos[2],obj.pos[1]-self.pos[1]),math.atan2(self.newVel[2]-(obj.vel[2] or obj.newVel[2]),self.newVel[1]-(obj.vel[1] or obj.newVel[1]))
    end
end

obj_mt.finishUpdateV=function(self)
    for i=1,2 do
        if (self.pos[i]<=self.radius and self.newVel[i]<0) or (self.pos[i]+self.radius>=love.graphics[i==1 and "getWidth" or "getHeight"]() and self.newVel[i]>0) then
            self.newVel[i]=-self.newVel[i]*0.8
        end
        self.vel[i]=self.newVel[i] or self.vel[i]
    end
end

obj_mt.updateV=function(self,nSpeed)
    if type(self.mass)=="number" then
        for k,v in pairs(tObj) do
            self:finishUpdateV()
        end
        for k,v in pairs(tObj) do
            local dist,ang,vAng=self:compare(v)
            if v~=self and type(v.mass)=="number" and type(dist)=="number" then
                if dist>self.radius+v.radius then
                    local nForce=(G*self.mass*v.mass)/dist^2
                    local xF,yF=math.cos(ang)*nForce,math.sin(ang)*nForce
                    self.newVel[1]=self.newVel[1]+xF*(nSpeed or 1)/self.mass
                    self.newVel[2]=self.newVel[2]+yF*(nSpeed or 1)/self.mass
                elseif math.abs((vAng-ang+math.pi)%(2*math.pi)-math.pi)<=math.pi/2 then
                    local combinedXVel,combinedYVel=(self.newVel[1]+v.vel[1])/2,(self.newVel[2]+v.vel[2])/2
                    local relativeVel=((self.newVel[1]-v.vel[1])^2+(self.newVel[2]-v.vel[2])^2)^0.5
                    local velTowardsObj,velLeftObj=math.cos(ang-vAng)*relativeVel,math.sin(ang-vAng)*relativeVel
                    self.newVel[1]=(math.cos(ang+math.pi)*velTowardsObj+math.cos(ang-math.pi/2)*velLeftObj)/2*0.8+combinedXVel
                    self.newVel[2]=(math.sin(ang+math.pi)*velTowardsObj+math.sin(ang-math.pi/2)*velLeftObj)/2*0.8+combinedYVel
                end
            end
        end
    end
end

obj_mt.updateP=function(self,nSpeed)
    self:finishUpdateV()
    self.pos[1]=(self.newPos[1] or self.pos[1])+self.vel[1]*(nSpeed or 1)
    self.pos[2]=(self.newPos[1] or self.pos[2])+self.vel[2]*(nSpeed or 1)
end

function love.load()
    _elapsed=0
    tObj=setmetatable({},{
        __newindex=function(self,index,value)
            rawset(self,index,type(value)=="table" and setmetatable(value,{__index=function(self,index) return obj_mt[index] end}) or value)
        end
    })

    tObj[1]={pos={100,100},vel={},mass=500000,radius=10,col={255,0,0},newPos={},newVel={0.0002,0}}
    tObj[2]={pos={100,200},vel={},mass=500000,radius=10,col={0,255,0},newPos={},newVel={-0.0002,0}}
    tObj[3]={pos={150,200},vel={},mass=500000,radius=10,col={0,0,255},newPos={},newVel={0.00005,0}}
    --tObj[4]={pos={150,500},vel={},mass=500000,radius=5,col={255,0,255},newPos={},newVel={0.00005,0}}
end

function love.update(dt)
    if not bPaused then
        _elapsed=_elapsed+dt
        for k,v in pairs(tObj) do
            v:updateV(frameskip)
        end
        for k,v in pairs(tObj) do
            v:updateP(frameskip)
        end
    end
end

function printLine(sText)
    sText=tostring(sText)
    if type(sText)=="string" then
        love.graphics.print(sText,0,at)
    end
    at=at+12
end

function love.draw()
    at=0
    love.graphics.setColor(255,255,255)
    printLine(math.floor(_elapsed),0,0)
    for k,v in pairs(tObj) do
        if v.col and #v.col==3 then
            love.graphics.setColor(unpack(v.col))
        else
            love.graphics.setColor(255,255,255)
        end
        love.graphics.circle("fill",v.pos[1],v.pos[2],v.radius,v.radius*math.pi)
    end
end

function love.run()

    math.randomseed(os.time())
    math.random() math.random()

    if love.load then love.load(arg) end

    local dt = 0

    -- Main loop time.
    while true do
        -- Process events.
        if love.event then
            love.event.pump()
            for e,a,b,c,d in love.event.poll() do
                if e == "quit" then
                    if not love.quit or not love.quit() then
                        if love.audio then
                            love.audio.stop()
                        end
                        return
                    end
                end
                love.handlers[e](a,b,c,d)
            end
        end

        -- Update dt, as we'll be passing it to update
        if love.timer then
            love.timer.step()
            dt = love.timer.getDelta()
        end

        -- Call update and draw
        if love.update then
            for run=1,math.floor(emulationSpeed/frameskip) do
                love.update(dt*frameskip/emulationSpeed)
            end
        end -- will pass 0 if love.timer is disabled
        if love.graphics then
            love.graphics.clear()
            if love.draw then love.draw() end
        end
        if love.timer then love.timer.sleep(0.001) end
        if love.graphics then love.graphics.present() end
    end
end