DragonRuby Game Toolkit: Easing Fubar

main.rb

def tick args
  duration = 120
  args.state.after_image_queue ||= []
  args.state.start_at = if Kernel.tick_count == 0
                          0
                        elsif Kernel.tick_count.zmod?(duration.idiv(2))
                          args.state.start_at + duration.idiv(2)
                        else
                          args.state.start_at
                        end

  # fiddle with these numbers
  fiddle_x_1 = 1
  fiddle_x_2 = 5
  if Kernel.tick_count % duration < duration.idiv(2)
    perc = Easing.smooth_stop(start_at: args.state.start_at,
                              duration: duration.idiv(2),
                              tick_count: Kernel.tick_count,
                              power: 1)
    start_x = 0
    add_x = 320
    pow_x = fiddle_x_1 + fiddle_x_2 * perc
    start_y = 0
    add_y = 320
  else
    perc = Easing.smooth_stop(start_at: args.state.start_at,
                              duration: duration.idiv(2),
                              tick_count: Kernel.tick_count,
                              power: 1, flip: true)
    start_x = 640
    add_x = -320
    pow_x = fiddle_x_1 + fiddle_x_2 * perc
    start_y = 0
    add_y = 320
  end

  s = { x: start_x + add_x * perc ** pow_x,
        y: start_y + add_y * perc,
        w: 32,
        h: 32,
        path: :solid,
        r: 0,
        g: 0,
        b: 0,
        anchor_x: 0.5,
        anchor_y: 0.5 }

  if Kernel.tick_count.zmod?(2)
    args.state.after_image_queue << { at: Kernel.tick_count,
                                      sprite: s,
                                      duration: 60 }
  end

  args.state.after_image_queue.reject! { |h| h.at.elapsed_time > h.duration }

  args.outputs.sprites << s
  args.outputs.sprites << args.state.after_image_queue.map do |h|
    perc = Easing.smooth_start(start_at: h.at,
                               duration: h.duration,
                               tick_count: Kernel.tick_count,
                               power: 2,
                               flip: 1)
    h.sprite.merge(a: perc * 255)
  end
en