Well done on posting this! it's a great way to learn and share your experience of learning new languages and get feedback. (just take the comments by face value without any sentiments, you should learn from them, not make them discourage you, ignore "my eyes are bleeding" type of comments or "Scala is sooo complexxx" unless they have some really constructive criticism in them...)

One tiny cosmetic suggestion that popped to my eyes since you asked for comments :)

    def parseInputRange (s: String): Array[Int] = {
      val ab = s.split(":").map(_.toInt)
      (ab(0) to ab(1)).toArray
    }

the `to` method is inclusive on the end of the range, so it is the same as until x + 1

Good luck!