physics

local part = Instance.new("Part", script)
part.Size = Vector3.new(10, 6, .1)
part.Position = Vector3.new(-10, 5, -10)
part.Anchored = true
part.Material = "Glass"
part.Transparency = .5

local sf = Instance.new("SurfaceGui", part)
sf.Face = "Front"
sf.ClipsDescendants = false
local backg = Instance.new("Frame", sf)
backg.Size = UDim2.new(1, 0, 1, 0)
backg.BackgroundColor3 = Color3.new()
s_size = backg.AbsoluteSize

local t_back = Instance.new("TextBox", sf)
t_back.Position = UDim2.new(1, 0, 0, 0)
t_back.Size = UDim2.new(0, 400, 1, 0)
t_back.BackgroundColor3 = Color3.new(.2, .2, .2)
t_back.TextScaled = true
t_back.TextXAlignment = 0
t_back.TextYAlignment = 0

-- the

local s = [[

local sf = script.Parent.SurfaceGui
local s_size = sf.Frame.AbsoluteSize
-- settings

settings = {}
settings.g = Vector2.new(0, 0)
settings.fps = 60
settings.wrapx = false
settings.wrapy = false
settings.boundx = true
settings.boundy = true

-- physics functions

function addforce(ob, f)
    ob.acc += f/ob.mass
end

function grav(one, two, g)
    local the = two.pos - one.pos
    local g_force = one.mass*two.mass*g/the.Magnitude^2
    local forc = the / the.Magnitude * g_force
    addforce(one, forc)
end

function upd(ob, dt)
    dt = dt or 1
    addforce(ob, settings.g)
    ob.vel += ob.acc*dt
    ob.pos += ob.vel*dt
    if settings.wrapx then
        ob.pos = Vector2.new(ob.pos.X % s_size.X, ob.pos.Y)
    end
    if settings.wrapy then
        ob.pos = Vector2.new(ob.pos.X, ob.pos.Y % s_size.Y)
    end
    if settings.boundx then
        ob.pos = ob.pos:Max(Vector2.new(ob.size.X/2, -math.huge))
        ob.pos = ob.pos:Min(Vector2.new(s_size.X - ob.size.X/2, math.huge))
    end
    if settings.boundy then
        ob.pos = ob.pos:Max(Vector2.new(-math.huge, ob.size.Y/2))
        ob.pos = ob.pos:Min(Vector2.new(math.huge, s_size.Y - ob.size.Y/2))
    end
    ob.acc = Vector2.new()
end

function show(ob)
    ob.vis.Position = UDim2.new(0, ob.pos.X, 0, ob.pos.Y)
    ob.vis.Rotation = ob.angle
    ob.vis.Size = UDim2.new(0, ob.size.X, 0, ob.size.Y)
end

function obj(x, y, s, a, m, v, ac)
    m = m or 1
    x = x or 0
    y = y or 0
    s = s or Vector2.new(20, 20)
    a = a or 0
    v = v or Vector2.new(0, 0)
    ac = ac or Vector2.new()
    local p = {}
    p.pos = Vector2.new(x, y)
    p.size = s
    p.angle = a
    p.mass = m
    p.vel = v
    p.acc = ac
    local vis = Instance.new("Frame", sf)
    vis.AnchorPoint = Vector2.new(.5, .5)
    vis.BackgroundColor3 = Color3.new(1,1,1)
    p.vis = vis
    return p
end
]]

local e = [[

load()

while true do
    update(task.wait(1/settings.fps))
end
]]

-- main stuff
local real = [[
local test1
local test2
local info

function checktouchedwall(ob)
    if ob.pos.X == ob.size.X/2 then
        return Vector2.new(1, 0)
    end
    if ob.pos.X == s_size.X - ob.size.X/2 then
        return Vector2.new(-1, 0)
    end
    if ob.pos.Y == ob.size.Y/2 then
        return Vector2.new(0, 1)
    end
    if ob.pos.Y == s_size.Y - ob.size.Y/2 then
        return Vector2.new(0, -1)
    end
end

function load()
    settings.boundx = true
    settings.boundy = true
  --obj(x, y, s, a, m, v, ac)
    test1 = obj(s_size.X/2, s_size.Y/2, false, false, false, false)
    test2 = obj(250, 350, false, false, false, false, false)
    test2.vel = Vector2.new(10, 40)
    info = Instance.new("TextBox", sf)
    info.Size = UDim2.new(0, 200, 0, 60)
    info.TextScaled = true
    info.TextXAlignment = 0
    info.BackgroundTransparency = 1
    info.TextColor3 = Color3.new(1,1,1)
    info.RichText = true
    table.foreach(test2, print)
end

function update(dt)
info.Text="vel: "..math.round(test2.vel.X)..", "..math.round(test2.vel.Y).."<br />".."pos: "..math.round(test2.pos.X)..", "..math.round(test2.pos.Y).."<br />".."grav: "..settings.g.X..", "..settings.g.Y.."<br />".."dt: "..dt

------------------- real stuff
    local normal = checktouchedwall(test2)
    if normal then
        test2.vel = test2.vel - 2*test2.vel:Dot(normal)*normal
    end
    grav(test2, test1, 600000)
    upd(test2, dt)
    show(test2)
    show(test1)
end
]]

t_back.Text = ""
t_back.PlaceholderText = real


-- executors
NS(s..real..e, part)