refactor: comply with GDScript style guide

I have rewritten my code to mostly comply with the Godot Doc's style
guide, mainly prefixing private variables with an underscore and code
order. One big exception is that I use 4 spaces instead of tabs for
better viewing in Github. In addition, I have elected to not prefix
public interface methods that are meant to be overriden with an
underscore. Also added Python-style docstrings and reduced the number of
magic constants. Per-level instructions have been added as well.

Author: danielzting

levels/bogo_sort.gd

@@ -1,9 +1,13 @@
-extends ComparisonSort
 class_name BogoSort
+extends ComparisonSort
 
-const TITLE = "BOGOSORT"
-const ABOUT = """Generates random permutations until the array is
-sorted."""
+const NAME = "BOGOSORT"
+const ABOUT = """
+Generates random permutations until the array is sorted.
+"""
+const CONTROLS = """
+Keep on hitting RIGHT ARROW to CONTINUE and hope for the best!
+"""
 
 func _init(array).(array):
     pass
@@ -13,6 +17,8 @@ func check(action):
 
 func next():
     array = ArrayModel.new(array.size)
+    if array.is_sorted():
+        emit_signal("done")
 
 func emphasized(i):
     return false

levels/bubble_sort.gd

@@ -1,34 +1,41 @@
-extends ComparisonSort
 class_name BubbleSort
+extends ComparisonSort
 
-const TITLE = "BUBBLE SORT"
-const ABOUT = """Bubble sort iterates through the array and looks at
-each pair of elements, swapping them if they are out of order. When it
-has gone through the entire array without swapping a single pair, it has
+const NAME = "BUBBLE SORT"
+const ABOUT = """
+Bubble sort iterates through the array and looks at each pair of
+elements, swapping them if they are out of order. When it has gone
+through the entire array without swapping a single pair, it has
 finished. Though simple to understand, bubble sort is hopelessly
-inefficient on all but the smallest of arrays."""
-var index = 0
-var swapped = false
+inefficient on all but the smallest of arrays.
+"""
+const CONTROLS = """
+If the two highlighted elements are out of order, hit LEFT ARROW to SWAP
+them. Otherwise, hit RIGHT ARROW to continue.
+"""
+
+var _index = 0
+var _swapped = false
 
 func _init(array).(array):
     pass
 
 func check(action):
-    if array.get(index) > array.get(index + 1):
-        return action == "swap"
+    if array.get(_index) > array.get(_index + 1):
+        return action == ACTIONS.SWAP
     else:
-        return action == "no_swap"
+        return action == ACTIONS.NO_SWAP
 
 func next():
-    if array.get(index) > array.get(index + 1):
-        array.swap(index, index + 1)
-        swapped = true
-    index += 1
-    if index == array.size - 1:
-        if not swapped:
+    if array.get(_index) > array.get(_index + 1):
+        array.swap(_index, _index + 1)
+        _swapped = true
+    _index += 1
+    if _index == array.size - 1:
+        if not _swapped:
             emit_signal("done")
-        index = 0
-        swapped = false
+        _index = 0
+        _swapped = false
 
 func emphasized(i):
-    return i == index or i == index + 1
+    return i == _index or i == _index + 1

levels/comparison_sort.gd

@@ -1,42 +1,54 @@
-extends Node
 class_name ComparisonSort
+extends Node
 
 signal done
 signal mistake
 
-const ACTIONS = ["swap", "no_swap"]
+enum ACTIONS {SWAP, NO_SWAP}
+
+const DISABLE_TIME = 1.0
 
 var array: ArrayModel
-var timer = Timer.new()
 var active = true
 
+var _timer = Timer.new()
+
 func _init(array):
+    """Initialize array and timer."""
     self.array = array
-    timer.one_shot = true
-    timer.connect("timeout", self, "_on_Timer_timeout")
-    add_child(timer)
+    _timer.one_shot = true
+    _timer.connect("timeout", self, "_on_Timer_timeout")
+    add_child(_timer)
     self.connect("mistake", self, "_on_ComparisonSort_mistake")
 
+func _input(event):
+    """Pass input events for checking and take appropriate action."""
+    if not active:
+        return
+    for action in ACTIONS:
+        if event.is_action_pressed(action):
+            if check(ACTIONS[action]):
+                next()
+            else:
+                emit_signal("mistake")
+
 func check(action):
-    pass
+    """Determine if the given action enum value is correct."""
+    push_error("NotImplementedError")
 
 func next():
-    pass
+    """Advance the state by one step and signal done if completed."""
+    push_error("NotImplementedError")
+
+func emphasized(i):
+    """Return whether the given index should be highlighted."""
+    push_error("NotImplementedError")
 
 func _on_ComparisonSort_mistake():
+    """Disable the controls for one second."""
     active = false
-    timer.start(1)
+    _timer.start(DISABLE_TIME)
 
 func _on_Timer_timeout():
+    """Reenable the controls."""
     active = true
-
-func _input(event):
-    if not active:
-        return
-
-    for action in ACTIONS:
-        if event.is_action_pressed(action):
-            if check(action):
-                next()
-            else:
-                emit_signal("mistake")

levels/insertion_sort.gd

@@ -1,38 +1,46 @@
-extends ComparisonSort
 class_name InsertionSort
+extends ComparisonSort
 
-const TITLE = "INSERTION SORT"
-const ABOUT = """Insertion sort goes through the array and inserts each
+const NAME = "INSERTION SORT"
+const ABOUT = """
+Insertion sort goes through the array and inserts each
 element into its correct position. It is most similar to how most people
 would sort a deck of cards. It is also slow on large arrays but it is
 one of the faster quadratic algorithms. It is often used to sort smaller
-subarrays in hybrid sorting algorithms."""
-var end = 1
-var index = end
+subarrays in hybrid sorting algorithms.
+"""
+const CONTROLS = """
+Hit LEFT ARROW to SWAP the two highlighted elements as long as they are
+out of order. When this is no longer the case, hit RIGHT ARROW to
+advance.
+"""
+
+var _end = 1
+var _index = _end
 
 func _init(array).(array):
     pass
 
 func check(action):
-    if array.get(index - 1) > array.get(index):
-        return action == "swap"
+    if array.get(_index - 1) > array.get(_index):
+        return action == ACTIONS.SWAP
     else:
-        return action == "no_swap"
+        return action == ACTIONS.NO_SWAP
 
 func next():
-    if array.get(index - 1) > array.get(index):
-        array.swap(index - 1, index)
-        index -= 1
-        if index == 0:
+    if array.get(_index - 1) > array.get(_index):
+        array.swap(_index - 1, _index)
+        _index -= 1
+        if _index == 0:
             _grow()
     else:
         _grow()
 
 func _grow():
-    end += 1
-    if end == array.size:
+    _end += 1
+    if _end == array.size:
         emit_signal("done")
-    index = end
+    _index = _end
 
 func emphasized(i):
-    return i == index or i == index - 1
+    return i == _index or i == _index - 1

levels/selection_sort.gd

@@ -1,33 +1,41 @@
-extends ComparisonSort
 class_name SelectionSort
+extends ComparisonSort
+
+const NAME = "SELECTION SORT"
+const ABOUT = """
+Selection sort incrementally builds a sorted array by repeatedly looking
+for the smallest element and swapping it onto the end of the sorted
+portion of the array, which initially starts with size zero but grows
+after each round. It is faster than an unoptimized bubble sort but
+slower than insertion sort.
+"""
+const CONTROLS = """
+Keep on hitting RIGHT ARROW until you encounter an element that is
+smaller than the left highlighted element, then hit LEFT ARROW to swap
+the new smallest into place and keep going.
+"""
 
-const TITLE = "SELECTION SORT"
-const ABOUT = """Selection sort incrementally builds a sorted array by
-repeatedly looking for the smallest element and swapping it onto the
-end of the sorted portion of the array, which initially starts with size
-zero but grows after each round. It is faster than an unoptimized bubble
-sort but slower than insertion sort."""
-var base = 0
-var index = base + 1
+var _base = 0
+var _index = _base + 1
 
 func _init(array).(array):
     pass
 
 func check(action):
-    if array.get(base) > array.get(index):
-        return action == "swap"
+    if array.get(_base) > array.get(_index):
+        return action == ACTIONS.SWAP
     else:
-        return action == "no_swap"
+        return action == ACTIONS.NO_SWAP
 
 func next():
-    if array.get(base) > array.get(index):
-        array.swap(base, index)
-    index += 1
-    if index == array.size:
-        base += 1
-        index = base + 1
-    if base == array.size - 1:
+    if array.get(_base) > array.get(_index):
+        array.swap(_base, _index)
+    _index += 1
+    if _index == array.size:
+        _base += 1
+        _index = _base + 1
+    if _base == array.size - 1:
         emit_signal("done")
 
 func emphasized(i):
-    return i == index or i == base
+    return i == _index or i == _base

models/array_model.gd

@@ -1,29 +1,34 @@
 """
-A plain old one-dimensional random access array.
+A plain old one-dimensional random access array wrapper around the
+built-in class.
 """
 
-extends Reference
 class_name ArrayModel
+extends Reference
 
 var array = []
-var size
+var size = 0
 
-func _init(size):
+func _init(size=16):
+    """Randomize the array."""
     for i in range(1, size + 1):
         array.append(i)
     array.shuffle()
     self.size = size
 
 func get(i):
+    """Retrieve the value of the element at index i."""
     return array[i]
 
 func is_sorted():
+    """Check if the array is in monotonically increasing order."""
     for i in range(size - 1):
         if array[i] > array[i + 1]:
             return false
     return true
 
 func swap(i, j):
+    """Swap the elements at indices i and j."""
     var temp = array[i]
     array[i] = array[j]
     array[j] = temp

project.godot

@@ -64,7 +64,8 @@ config/icon="res://assets/icon.png"
 
 [autoload]
 
-scene="*res://scripts/scene.gd"
+GlobalScene="*res://scripts/scene.gd"
+GlobalTheme="*res://scripts/theme.gd"
 
 [display]
 
@@ -116,12 +117,12 @@ ui_down={
 , Object(InputEventJoypadButton,"resource_local_to_scene":false,"resource_name":"","device":0,"button_index":13,"pressure":0.0,"pressed":false,"script":null)
  ]
 }
-swap={
+SWAP={
 "deadzone": 0.5,
 "events": [ Object(InputEventKey,"resource_local_to_scene":false,"resource_name":"","device":0,"alt":false,"shift":false,"control":false,"meta":false,"command":false,"pressed":false,"scancode":16777231,"unicode":0,"echo":false,"script":null)
  ]
 }
-no_swap={
+NO_SWAP={
 "deadzone": 0.5,
 "events": [ Object(InputEventKey,"resource_local_to_scene":false,"resource_name":"","device":0,"alt":false,"shift":false,"control":false,"meta":false,"command":false,"pressed":false,"scancode":16777233,"unicode":0,"echo":false,"script":null)
  ]

scenes/levels.tscn

@@ -68,15 +68,15 @@ margin_right = 1352.0
 margin_bottom = 352.0
 custom_constants/separation = 50
 
-[node name="Description" type="Label" parent="LevelSelect/Preview/InfoBorder/Info"]
+[node name="About" type="Label" parent="LevelSelect/Preview/InfoBorder/Info"]
 margin_right = 810.0
 margin_bottom = 332.0
 rect_min_size = Vector2( 810, 0 )
 size_flags_vertical = 3
 text = "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Suspendisse luctus lorem felis, in imperdiet mauris faucibus in. Vestibulum interdum mi at arcu congue congue. Cras sodales mauris odio, eget iaculis dolor tempor quis. Suspendisse nec iaculis sapien, eu sollicitudin orci. Nulla volutpat pellentesque ex nec cursus."
 autowrap = true
 
-[node name="Instructions" type="Label" parent="LevelSelect/Preview/InfoBorder/Info"]
+[node name="Controls" type="Label" parent="LevelSelect/Preview/InfoBorder/Info"]
 margin_left = 860.0
 margin_right = 1332.0
 margin_bottom = 332.0