add: basic virus implementation

growth/virus.gd

@@ -1,16 +1,52 @@
 extends Node2D
 
-@export var speed = 400 # How fast the player will move (pixels/sec).
+@export var speed = 400 # How fast the virus will move (pixels/sec).
+@export var attack_range = 200 # virus vision radius (pixels)
+
+# a virus is instantiated as Spawning and transitions (matures) into Spawned
+# after a timer timeout, after which it is activated and ready to do its thing.
+enum SpawningState {Spawning, Spawned}
+# when idle, a virus Waits. if it has already performed some action, it may
+# become Blocked for a while. otherwise it might be Running. like a process.
+enum ActionState {Blocked, Waiting, Running}
+
+var spawning_state
+var action_state
+
+var targets # who the virus will attack
 
 func _ready():
-	# Initalize with random abilities from available abilities
+	self.spawning_state = SpawningState.Spawning
+	self.action_state = ActionState.Waiting
 
 func _process(delta):
-	# Grow in size
-	
-	# RayCast towards player (every N frames), moving towards it if close enough
-	# Or should we always move towards the player?
-	
-	# Use abilities if:
-	## Raycast hit
-	## Regular intervals (if close enough to player)?
+	if self.spawning_state != SpawningState.Spawned:
+		return # do nothing if not yet spawned
+	if len(self.targets) == 0:
+		return # do nothing if no set targets
+
+	# --- determine nearest target
+	var nearest_target = self.targets[0] 
+	var shortest_distance = 0
+	for i in range(1, len(self.targets)):
+		var target = self.targets[i]
+		var distance = self.position.distance_to(target)
+		if distance < shortest_distance:
+			shortest_distance = distance
+			nearest_target = target
+
+	# --- attack the nearest target, if within range
+	if self.action_state != ActionState.Blocked:
+		if shortest_distance < self.attack_range:
+			self.attack(nearest_target)
+
+	# --- move towards nearest target
+	self.position += \
+		self.position.direction_to(nearest_target) * self.speed * delta
+
+func attack(target):
+	# do attack, block until timer
+	self.action_state = ActionState.Blocked
+
+func _on_mature():
+	spawning_state = SpawningState.Spawned