feat: add sound effects

The player can now enjoy optional synthesized sound whose pitch is
derived from the elements being compared.

Author: danielzting

levels/bogo_sort.gd

@@ -19,3 +19,6 @@ func next(action):
 
 func get_effect(i):
     return EFFECTS.NONE
+
+func get_frac():
+    return array.frac(0)

levels/bubble_sort.gd

@@ -48,3 +48,6 @@ func get_effect(i):
     if i >= _end:
         return EFFECTS.DIMMED
     return EFFECTS.NONE
+
+func get_frac():
+    return (array.frac(_index) + array.frac(_index + 1)) / 2.0

levels/cocktail_sort.gd

@@ -56,3 +56,6 @@ func get_effect(i):
     if i < _sorted and _forwards == true or i < _sorted - 1 or i >= array.size - _sorted:
         return EFFECTS.DIMMED
     return EFFECTS.NONE
+
+func get_frac():
+    return (array.frac(_index) + array.frac(_index + 1)) / 2.0

levels/comb_sort.gd

@@ -46,3 +46,6 @@ func get_effect(i):
     if i >= _end:
         return EFFECTS.DIMMED
     return EFFECTS.NONE
+
+func get_frac():
+    return (array.frac(_index) + array.frac(_index + _gap)) / 2.0

levels/cycle_sort.gd

@@ -48,3 +48,6 @@ func get_effect(i):
 
 func get_pointer():
     return _pointer
+
+func get_frac():
+    return array.frac(_index)

levels/insertion_sort.gd

@@ -50,3 +50,6 @@ func _grow():
     if _end == array.size:
         emit_signal("done")
     _index = _end
+
+func get_frac():
+    return (array.frac(_index - 1) + array.frac(_index)) / 2.0

levels/merge_sort.gd

@@ -82,3 +82,10 @@ func _get_middle():
 func _get_end():
     """Get the index of one past the right subarray's tail."""
     return _sub_no * _sub_size + _sub_size
+
+func get_frac():
+    if _left == _get_middle():
+        return array.frac(_right)
+    if _right == _get_end():
+        return array.frac(_left)
+    return (array.frac(_left) + array.frac(_right)) / 2.0

levels/odd_even_sort.gd

@@ -40,3 +40,6 @@ func get_effect(i):
     if i == _index or i == _index + 1:
         return EFFECTS.HIGHLIGHTED
     return EFFECTS.NONE
+
+func get_frac():
+    return (array.frac(_index) + array.frac(_index + 1)) / 2.0

levels/quick_sort.gd

@@ -77,3 +77,6 @@ func get_effect(i):
 
 func get_pointer():
     return _pointer
+
+func get_frac():
+    return array.frac(_index)

levels/selection_sort.gd

@@ -52,3 +52,6 @@ func get_effect(i):
 
 func get_pointer():
     return _min
+
+func get_frac():
+    return array.frac(_index)