DragonRuby collision and physics

main.rb

def tick args
  # initialization
  args.state.x             ||= 620
  args.state.y             ||= 700
  args.state.dy            ||= 0
  args.state.dx            ||= 25
  args.state.gravity         = -0.5
  args.state.drag_coeff      = 0.05
  args.state.walls           = [
    [0, 0, 1280, 100],
    [800, 0, 100, 720]
  ]
  args.state.elasticity      = 0.6
  args.state.entropy_limit   = 2

  # render
  args.outputs
      .solids << [0, 0, 1280, 720, 32, 32, 32]

  args.outputs
      .labels << [10, 680,
                  "dy: #{args.state.dy}",
                  255, 255, 255]

  final_dy = args.state.dy.abs *
             (args.state.drag_coeff ** 2)

  args.outputs
      .labels << [10, 650,
                  "drag_coeff: #{final_dy}",
                  255, 255, 255]

  args.outputs
      .sprites << [args.state.x, args.state.y,
        20, 20, 'sprites/square-orange.png']

  args.outputs
      .solids << args.state.walls

  # simulation
  # gravity
  args.state.y  += args.state.dy
  args.state.dy += args.state.gravity
  args.state.dy += final_dy

  # power
  args.state.x  += args.state.dx
  args.state.dx *= 0.9

  # ground collision

  # right of box
  collided_right = args.state
                       .walls
                       .find_all { |w| w.x > args.state.x }
                       .find { |w| [args.state.x,
                                    args.state.y, 20, 20].intersect_rect? w }

  if collided_right
    args.state.x   = collided_right.left - 20
    args.state.dx  = args.state.dx * -1 *
                     args.state.elasticity
  end

  # below box
  collided_floor = args.state
                       .walls
                       .find_all { |w| w.y < args.state.y }
                       .find { |w| [630, args.state.y, 20, 20].intersect_rect? w }

  # collision
  if collided_floor
    args.state.y   = collided_floor.top
    args.state.dy  = args.state.dy * -1 *
                     args.state.elasticity

    # entropy after collision
    reached_entropy = (
      args.state.dy.abs <
      args.state.entropy_limit
    )

    args.state.dy = 0 if reached_entropy
  end

  # tunneling
  args.state.y   = 700 if args.state.y < 0
end

$gtk.reset