use ability keys instead of indices

src/entity.js

@@ -6,7 +6,7 @@ import Team from './team.js'
 
 export default class Entity {
   id = crypto.randomUUID()
-  abilities = [null, null, null, null] // TODO: do something about this being an array...
+  abilities = {}
   casting = null
   cooldowns = {}
   dead = false
@@ -266,7 +266,7 @@ export default class Entity {
 
     if (this.#attacking) {
       const cursor = this.#dest ?? this.position
-      const basicAttack = this.ability(0)
+      const basicAttack = this.ability('a')
       if (basicAttack != null) {
         const target = this.closestTargetTo(cursor, 500)
         if (target != null && this.distanceTo(target.position) < basicAttack.range + this.radius + target.radius) {
@@ -275,7 +275,7 @@ export default class Entity {
           const timestamp = this.game?.currentTick ?? 0
           if (lastCast != null && lastCast + cooldown > timestamp) { return false }
 
-          this.castAction(0, cursor, false)
+          this.castAction('a', cursor, false)
           return true
         }
       }