Ninja: Tweak AI.

library/npc_ai/NinjaAI.gd

@@ -14,6 +14,8 @@ const HP_BAR := [
 	[Game_DungeonSize.CENTER_X + 1, Game_NinjaData.MAX_X],
 	[Game_NinjaData.MIN_X, Game_DungeonSize.CENTER_X],
 ]
+const COMMON_HORIZONTAL_GAP := 2
+const SHADOW_HORIZONTAL_GAP := 0
 
 var _end_game := false
 
@@ -47,13 +49,13 @@ func _ninja_act() -> void:
 			Game_NinjaData.ATTACK_RANGE):
 		hit_pc = true
 	elif _self_pos.y == Game_NinjaData.GROUND_Y:
-		# Try to jump and hit PC when standing on ground.
-		move_result = _try_move_vertically(Game_CoordCalculator.UP)
-		has_moved = move_result[0]
-		hit_pc = move_result[1]
-		# Otherwise try to move horizontally.
+		# Try to move horizontally when standing on ground.
+		has_moved = _try_move_horizontally(COMMON_HORIZONTAL_GAP)
+		# Otherwise try to jump and hit PC.
 		if not has_moved:
-			has_moved = _try_move_horizontally()
+			move_result = _try_move_vertically(Game_CoordCalculator.UP)
+			has_moved = move_result[0]
+			hit_pc = move_result[1]
 	else:
 		# UPDATE: Do not move horizontally in mid-air. Ninjas are close to each
 		# other in this way and PC can kill them easily.
@@ -90,7 +92,7 @@ func _shadow_ninja_act() -> void:
 	var is_vertical := true
 
 	if _self_pos.y == Game_NinjaData.GROUND_Y:
-		has_moved = _try_move_horizontally()
+		has_moved = _try_move_horizontally(SHADOW_HORIZONTAL_GAP)
 		is_vertical = false
 	else:
 		move_result = _try_move_vertically(Game_CoordCalculator.DOWN)
@@ -146,10 +148,13 @@ func _try_move_vertically(direction: int) -> Array:
 	return [true, is_pc]
 
 
-func _try_move_horizontally() -> bool:
+func _try_move_horizontally(min_range: int) -> bool:
 	var pos := Game_ConvertCoord.sprite_to_coord(_self)
 	var move_to: Game_IntCoord
 
+	if abs(pos.x - _pc_pos.x) <= min_range:
+		return false
+
 	if pos.x < _pc_pos.x:
 		move_to = Game_IntCoord.new(pos.x + 1, pos.y)
 	elif pos.x > _pc_pos.x:

user/doc/ninja.md

@@ -95,7 +95,7 @@ A common ninja may perform one of three actions at the start of his turn.
 
 Action 1. Hit PC if he is adjacent to PC. His symbol changes from n to x for one turn.
 
-Action 2. When on ground, jump up if there is at least one unoccupied grid above. Otherwise, if he is not in the same column with PC, try to move 1 step horizontally towards PC. A ninja can jump at most 2 grids high. PC is hit if he blocks the jumping path. If another NPC blocks the vertical or horizontal path, the ninja cannot move to his destination.
+Action 2. When on ground, if he is more than 2 steps away from PC horizontally, try to move 1 step towards PC. Otherwise, jump up if there is at least one unoccupied grid above. A ninja can jump at most 2 grids high. PC is hit if he blocks the jumping path. If another NPC blocks the vertical or horizontal path, the ninja cannot move to his destination.
 
 Action 3. When in mid-air, try to fall down 2 grids. Same as action 2, PC is hit if he blocks the way, and the ninja can be blocked by his allies.