we have a gauge! next up, let's style the page

app/presenters/gauge_presenter.rb

@@ -0,0 +1,34 @@
+class GaugePresenter
+  def initialize(scale:, score:)
+    @scale = scale
+    @score = score
+  end
+
+  def title
+    zone.type.to_s.capitalize
+  end
+
+  def color_class
+    "fill-#{zone.type}"
+  end
+
+  def score_percentage
+    percentage_for @score
+  end
+
+  def key_benchmark_percentage
+    percentage_for @scale.approval_zone.low_benchmark
+  end
+
+  private
+
+  def zone
+    @scale.zone_for_score(@score)
+  end
+
+  def percentage_for(number)
+    scale_minimum = @scale.warning_zone.low_benchmark
+    scale_maximum = @scale.ideal_zone.high_benchmark
+    (number - scale_minimum) / (scale_maximum - scale_minimum)
+  end
+end