Why I think scalatutorials.com uses the wrong way to teach Scala

1_Good parts

Step by step tutorial, the UX, and the worksheet are great. 
(Although the worksheet did not run for some of the lessons on my Chrome, Ubuntu 14.04)

2_Introduction

Scala Tutorials does not have an introduction to Scala. 
It starts with some arithmetic operations. 
This gives the idea that the whole tutorial will be a conversion guide from Java to Scala.

By contrast Twitter Scala School starts with a brief but important introduction.

* Why Scala?
* Think Scala
Scala is not just a nicer Java. 
You should learn it with a fresh mind- you will get more out of these classes.

3_vars_and_loops.scala

/*It seems to be a tiny detail but teaching vars(Lesson 3) before vals(Lesson 4) 
does not match the "importance" of them. And naming vals(values) as final variables makes us be 
certain that this is just a conversion guide from Java to Scala. 
Combined with "for loops"(Lesson  18) your junior devs will likely produce the horrible code below.*/

case class C(age: Int)

val list = List(C(1), C(2), C(3))

var sum = 0  
for ( i <- 0 until list.length) {  
  var item = list(i)
  sum +=  item.age
}  
println(sum)  

4_loops_without_loops.scala

/*The below code is the only sample for "Loops without loops"(Lesson 19)*/

(0 until 10).sum

/*You should teach higher order functions first. 
And you should show how they are important for functional combinators in collections.
Twitter Scala School does this quite well. 
http://twitter.github.io/scala_school/collections.html*/

5_match_as_a_switch.scala

/*Lesson 21 has the title "Match as a Switch". I suggest changing the title. 
Teach pattern matching with case classes and the Option type and with its other use cases.
*/

6_do_not_teach_loops.scala

/*Do not teach them loops. Teach them for comprehensions with collections, 
with the Option type(which is also a collection) and the Future type, and etc.
Make them have at least a little understanding of what a Monad is. 
And ensure that they understand the danger in the code below.*/

var x = 0
async { x = x + 1 }
async { x = x * 2 }