In its current form, Hedy consists of 14 different levels. The levels loosely follow the lesson series Python in de klas ("Python in the classroom") in such a way that these existing lessons can be executed with Hedy instead of with Python.
At the first level, students can firstly print text. For this, no
syntactic elements are needed other than the keyword [print]
followed by arbitrary text. Furthermore students can ask for
input of the user using the keyword [ask]. Here we decided to use
the keyword [ask] rather than [input] because it is more aligned
with what the role of the keyword is in the code than with what it
does. Input of a user can be repeated with [echo], so very simple
programs can be created in which a user is asked for a name or a
favorite animal, fulfilling Design Goal 6.
At the second level, variables are added to the syntax. Defining a variable is done with the word [is] rather than the equals symbol fulfilling Design Goal 3 and Design Goal 4.
In level 3 we add the option to create lists and retrieve elements, including random elements from lists with [at]. Adding lists and especially adding the option to select a
random item from a list allows for the creation of more interesting programs such as a guessing game, a story with random elements, which is an assignment from Python in de klas ("Python in the classroom"), or a customized dice.
In Level 3 the first syntactic element is introduced: the use of quotation marks to distinguish between strings and text. In teaching novices we have seen that this distinction can be confusing for a long time, so offering it early might help to draw attention to the fact that
computers need information about the types of variables. This level is thus an interesting combination of explaining syntax and explaining
programming concepts, which underlines their interdependency. The variable syntax using [is] remains unchanged, meaning that learners
can now use both [number is 12] and [name is Hedy].
In Level 5, selection with the if statement is introduced, but the
syntax is 'flat', i.e. placed on one line, resembling a regular syntax
more:
[if name is print ]
Else statements are also included, and are also placed on one line,
using the keyword [else]:
[if name is print else print ].
In Level 5, students learn to calculate with variables, so addition,
multiplication, subtraction and division are introduced. While this
might seem like a simple step, our experience taught us that the use of
[*] for multiplication, rather than
In working with non-English native Python novices. Research has found
the keyword [for] to be a confusing word for repetition, especially
because it sounds like the word 'four' [@hermans_code_2018]. For our
first simplest form, according to Design Goal 2, we opt to use
Quorum [@stefik_quorum_2017] syntax [repeat x times]. In this
initial form, like the if the syntax is placed on one line:
[repeat 5 times print ]
After Level 6, there is a clear need to 'move on', as the body of a loop (and also that of an if) can only consist of one line, which limits the possibilities of programs that users can create. We assume this limitation will be a motivating factor for learners, rather than 'having to learn' the block structure of Python, they are motivated by the prospect of building larger and more interesting programs (Design Goal 6). The syntax of the loop remains otherwise unchanged as per Design Goal 3, so the new form is:\
repeat 5 times
print 'Hello'
print 'I am repeated 5 times'
To allow for enough interleaving of concepts (Design Goal 5), we defer the introduction of syntax concepts for now, and focus on more conceptual additions: the nesting of blocks. We know indentation is a hard concept for students to learn, so this warrants its own level (Design Goal 3).
In level 9, learners the range syntax, looping over the values in a list with for animal in animals.
This allows the customization of stories, drawing and songs.
Once blocks are sufficiently automatized, learners will see a more
Python-like form of the for loop, namely: [for i in range 0 to 5].
This allows for access to the loop variable [i] and this allows for
more interesting programs, such as counting to 10. As per Design Goal 3,
the change is made small, and to do so (following Design Goal 4),
brackets and colons are deferred to a later level, but indentation which
was learned in Level 7 remains.
See for a discussion of fruther levels: #903
Learners are now allowed to use floats and need to place quotation marks around strings to distinguish them from numbers
In level 13, Learners learn about and and or in if statements.
In level 14, Learners learn about <(=) and >(=) in preparation for while loops.
In level 15, learners are introduced to the while loop. With the previous knowledge of booleans and < and >, learners can make basic while loops.
In this level, learners encounter different types of brackets for the first time, because it adds rectangular brackets for list access, which up to now was done with the keyword [at], following Design Goal 2. THis level also explain accessing lists with a numeric index, starting at 1. The code to access a specific
value has already been available technically since level 2, but there was no explanation yet how to access a specific value and it is not used in examples (and should maybe be removed?)
All levels allow for the use of comments, and it is up the the teachers to explain their different uses.
Leaving this here for now while refactoring the level structure further.
To make the step to full Python, learners will need to use the colon to denote the beginning of a block, in both loops and conditionals. Because blocks are already known, we can teach learners to use a colon before every indentation, and have them practice that extensively.
Level 11 adds round brackets in [print], [range] and
[input]. As per Design Goal 4, these are added as late as possible.
In level 13, booleans are added. Learners encounter True and False and how to use them in if statements
In level 19, learners are shown how to loop through a list. The length() function is also introduced, as it makes looping through a list easier. The code to loop through a list has already been available since the for loop was introduced but there was no explanation yet how to loop through the list.
In level 20, we introduce the = and ==. All variable assignments change is to =. All equality checks turn into ==.
In level 21, we introduce the != in the equality checks. This is introduced after the change to = and == as to make it easier to understand when you already know the syntax for =.
In level 22, we introduce <= and >=. This is introduced after the change to = and == as to make it easier to understand when you already know the syntax for =.