Swift class based fighting game

Dragon.swift

import Foundation

class Dragon: Enemy {
    let wings = 2
    override var type: String {
        "Dragon"
    }

    override init(strength: Int) {
        super.init(strength: strength * 2)
    }

    override func move() {
        print("\(type) flies forward.")
    }
}

Enemy.swift

import Foundation

class Enemy {
    var type: String {
        get {
            "Enemy"
        }
    }
    private(set) var health: Int = 100
    private let strength: Int

    init(strength: Int) {
        self.strength = strength
        print("A \(type) was born.")
    }
    init(strength: Int, healthBoost: Int) {
        health += healthBoost
        self.strength = strength
        print("A \(type) was born.")
    }

    func attack(_ x : Enemy) {
        if (Bool.random()) {
            print("\(type) hits \(x.type).")
            x.setDamage(strength)
        } else {
            print( Bool.random() ? "\(type) missed." : "\(x.type) dodged.")
        }
    }

    private func setDamage(_ x: Int) {
        health -= x
        if (health <= 0) {
            health = 0
            print("\(type) is dead.")
        } else {
            print("\(type) takes \(x) damage.")
        }
    }

    func move() {
        print("\(type) walks forward.")
    }
}

main.swift

let e1 = Skeleton(strength: Int.random(in: 5..<50))
let e2 = Dragon(strength: Int.random(in: 7..<50))
e1.move()
e2.move()
while e1.health != 0 && e2.health != 0 {
    e1.attack(e2)
    if (e2.health != 0) {
        e2.attack(e1)
    }
    print()
}

Skeleton.swift

import Foundation

class Skeleton: Enemy {
    override var type: String {
        "Skeleton"
    }

    override init(strength: Int) {
        super.init(strength: strength, healthBoost: 100)
    }

    override func move() {
        print("\(type) crawls forward.")
    }
}