Added Animator for creating animations with various tweeners, supports Gosu::Color's and numbers

lib/cyberarm_engine.rb

@@ -20,6 +20,7 @@ require_relative "cyberarm_engine/transform"
 require_relative "cyberarm_engine/ray"
 require_relative "cyberarm_engine/shader" if defined?(OpenGL)
 require_relative "cyberarm_engine/background"
+require_relative "cyberarm_engine/animator"
 
 require_relative "cyberarm_engine/text"
 require_relative "cyberarm_engine/timer"

lib/cyberarm_engine/animator.rb

@@ -0,0 +1,53 @@
+module CyberarmEngine
+  class Animator
+    DEFAULT_TWEEN = :linear
+    def initialize(start_time:, duration:, &block)
+      @start_time, @duration = start_time, duration
+      @block = block
+    end
+
+    def update
+      @block.call(self) if @block
+    end
+
+    def progress
+      (@start_time.to_f + (Gosu.milliseconds - @start_time)) / (@start_time + @duration.to_f)
+    end
+
+    def complete?
+      progress >= 1.0
+    end
+
+    def transition(from, to, tween = DEFAULT_TWEEN)
+      from + (to - from) * send("tween_#{tween}", progress)
+    end
+
+    def color_transition(from, to, tween = DEFAULT_TWEEN)
+      r = transition(from.red, to.red)
+      g = transition(from.green, to.green)
+      b = transition(from.blue, to.blue)
+      a = transition(from.alpha, to.alpha)
+
+      Gosu::Color.rgba(r, g, b, a)
+    end
+
+    def color_hsv_transition(from, to, tween = DEFAULT_TWEEN)
+      hue = transition(from.hue, to.hue, tween)
+      saturation = transition(from.saturation, to.saturation, tween)
+      value = transition(from.value, to.value, tween)
+      alpha = transition(from.alpha, to.alpha, tween)
+
+      Gosu::Color.from_ahsv(alpha, hue, saturation, value)
+    end
+
+    # NOTE: maybe use this for future reference? https://github.com/danro/easing-js/blob/master/easing.js
+
+    def tween_linear(t)
+      t
+    end
+
+    def tween_sine(t)
+      Math.sin(t) * t
+    end
+  end
+end