Physics.love

local nRuntime=0
local nBounces,rot=0
local tObjects={}
local nSpeed=50
local fps=0
local tFrames={}
local g=6.674*10^-11 -- in (m/kg)^2
local lastKey="none"
local lastUni=0

local function returnlist(...)
    return ...
end

function love.keypressed(key,unicode)
    lastKey=key
    lastUni=unicode
    if key=="kp-" and nSpeed>5 then
        nSpeed=nSpeed-5
    elseif key=="kp+" and nSpeed<100 then
        nSpeed=nSpeed+5
    elseif key=="insert" then
        table.insert(tObjects,{
            pos={
                x=math.random(1,love.graphics.getWidth()),
                y=math.random(1,love.graphics.getHeight())
            },
            look={
                radius=5,
                color={
                    math.random(0,255),
                    math.random(0,255),
                    math.random(0,255)
                }
            },
            vel={
                x=0,
                y=0
            },
            bounce=0.5,
            bounces=0,
            grav=10^math.random(10,11),
            trail={}
        })
    elseif key=="delete" then
        tObjects[#tObjects]=nil
    end
end

function love.update(nSecs)
    table.insert(tFrames,1,nSecs)
    tFrames[11]=nil
    local totTime=0
    for i=1,#tFrames do
        totTime=totTime+tFrames[i]
    end
    fps=#tFrames/totTime
    for run=1,nSpeed do
        for k,v in pairs(tObjects) do
            if run%10==1 then
                table.insert(v.trail,1,{x=v.pos.x,y=v.pos.y})
                v.trail[100]=nil
            end
            v.vel.newx=v.vel.x
            v.vel.newy=v.vel.y
            v.pos.x=v.pos.x+v.vel.newx*nSecs
            v.pos.y=v.pos.y+v.vel.newy*nSecs
            local bBounced=false
            for a,b in pairs(tObjects) do
                if b~=v and v.grav and b.grav then
                    local dx,dy=b.pos.x-v.pos.x,b.pos.y-v.pos.y
                    local nDist=(dx^2+dy^2)^0.5
                    local accel=((g*v.grav*b.grav)/(nDist))/v.grav
                    local nAng=math.atan2(dy,dx)
                    if nDist>0 then
                        v.vel.newx=v.vel.newx+accel*math.cos(nAng)*nSecs
                        v.vel.newy=v.vel.newy+accel*math.sin(nAng)*nSecs
                    end
                end
            end
            --[[for a,b in pairs(tObjects) do
                if b~=v then
                    local dx,dy=b.pos.x-v.pos.x,b.pos.y-v.pos.y
                    local dvx,dvy=v.vel.x-b.vel.x,v.vel.y-b.vel.y
                    local nDist=(dx^2+dy^2)^0.5
                    relVel=(dvx^2+dvy^2)^0.5
                    local rD=(math.atan2(dy,dx)-math.atan2(dvy,dvx))%(math.pi*2)
                    rot=k==1 and rD or rot
                    if nDist<=v.look.radius+b.look.radius and (rD<math.pi/2 or rD>math.pi*3/2) then
                        local nBounce=v.bounce*b.bounce
                        v.vel.newx=(v.grav*v.vel.newx+b.grav*b.vel.x)*nBounce/(v.grav+b.grav)
                        v.vel.newy=(v.grav*v.vel.newy+b.grav*b.vel.y)*nBounce/(v.grav+b.grav)
                        bBounced=true
                        v.bounces=v.bounces+1
                    end
                end
            end]]
        end
        for k,v in pairs(tObjects) do
            v.vel.x=v.vel.newx*(((v.pos.x-v.look.radius<=0 and v.vel.x<0) or (v.pos.x+v.look.radius>=love.graphics.getWidth() and v.vel.x>0)) and -1*v.bounce or 1)
            v.vel.y=v.vel.newy*(((v.pos.y-v.look.radius<=0 and v.vel.y<0) or (v.pos.y+v.look.radius>=love.graphics.getHeight() and v.vel.y>0)) and -1*v.bounce or 1)
        end
    end
end

function love.draw()
    for k,v in pairs(tObjects) do
        if type(v.look.color)=="table" then
            love.graphics.setColor(unpack(v.look.color))
        else
            love.graphics.setColor(returnlist(255,255,255))
        end
        for i=#v.trail,1,-1 do
            love.graphics.circle("fill",v.trail[i].x,v.trail[i].y,v.look.radius*i/#v.trail,v.look.radius*math.pi)
        end
        love.graphics.circle("fill",v.pos.x,v.pos.y,v.look.radius,v.look.radius*math.pi)
        --love.graphics.line(v.pos.x,v.pos.y,v.pos.x+v.vel.x*2,v.pos.y+v.vel.y*2)
    end
    love.graphics.setColor(255-math.ceil(200*fps/60),math.ceil(200*fps/60)+55,0)
    love.graphics.print("FPS: "..math.floor(fps).."/"..60,0,0)
    love.graphics.setColor(0,math.ceil(255*nSpeed/100),255-math.ceil(255*nSpeed/100))
    love.graphics.print("Emulation Speed: "..nSpeed.."/"..100,0,12)
    love.graphics.setColor(255,255,255)
    love.graphics.print("Objects: "..#tObjects,0,24)
    love.graphics.print("Key Name: "..lastKey,0,36)
    love.graphics.print("Key Unicode: "..lastUni,0,48)
end
tObjects[1]={
            pos={
                x=math.random(1,love.graphics.getWidth()),
                y=math.random(1,love.graphics.getHeight())
            },
            look={
                radius=10,
                color={
                    0,
                    0,
                    0
                }
            },
            vel={
                x=0,
                y=0
            },
            bounce=0.8,
            bounces=0,
            grav=10^12,
            trail={}
        }