Sunday, March 5, 2017

Phaser Girl JavaScript Lessons For a Middle School Girl

I'm working with girl coder on new drills based on Phaser and JavaScript. In each lesson, I sit by coder girl and watch her type in the same drill 10 times.

The philosophy for Phaser Girl is to take the simplest possible code snippet and build from there. Programming concepts are not explained until after the drills are started.  The idea is to dive in, start typing, and the concepts will arise over time.

This structure came from watching my son learn karate. Since his dojo (classroom) was 25 minutes away, I would often stay in the dojo and watch the class.

There are three components to teach kids karate:

  1. kihon (fundamental: punch, kick, block)
  2. kata (form: collection of kihon)
  3. kumite (sparring: application of kihon and kata)

For Phaser Girl, the equivalent is:

  1. syntax: conditionals, loops, variable assignment
  2. drills: the basis of Phaser Girl
  3. projects
Within this framework, I focus on drills. The syntax emerges from the drills.


I originally started with a target of 5 reps. During the first lesson, Blank Screen, I increased the target repetition to 10. The objective is for coder girl to be able to go through the drill without looking at reference material and without encountering a syntax error by rep 8.

By drill 6, Cursors, each rep was taking 5 minutes, pushing the total lesson time to 70 minutes. I gave coder girl a 5 minute break after rep 5.

Practical Application (kumite) Example

Level 1, simple project. 40 lines of code total.

Drill (kata) Example

Fundamental (kihon) Example

Monday, April 6, 2015

Komodo vs. PyCharm - Teenager Reviews Two Famous Python IDEs

by Kai of Palo Alto High School
As a fifteen-year old novice programmer who codes in Python, I tested two different editors, PyCharm Professional and the new Komodo IDE 9 that was just released.

When I first opened up PyCharm, I felt like it provides the maximum amount of features from the start. Initially, the crowded menu and taskbar were too much of a distraction as I could not figure out what many of the options actually did.  I liked that PyCharm gives me the ability to see the file path of the program I am editing. This is useful when I edit multiple programs at once, as it is easy to quickly distinguish one program from another. 

The other tools worked well and the ability to access old variables when writing new code is nice. My first impression of PyCharm was that it tried to be too versatile and sacrificed usability in the process.
When I opened up Komodo the first thing I noticed was the elegant presentation. The editor relies on alternating color schemes to make text easy to read. The entire window is taken up by the code you are editing. Additionally, the menu consisted of simple icons and pop-up menu’s that made editing and running my program a easy task.

A nice feature is that Komodo lets you know which function you are editing, a feature that would be nice to have in PyCharm. Two arrows at the top of the page allow you to revisit code you were previously editing.

This functionality is extremely helpful for longer pieces of code. Unfortunately, the icon based menu occasionally made it difficult to find what I are looking for. For example, I wanted the command to comment out a section of my code. Usually, it would be housed under the section of the menu called “Edit”. With Komodo there is no such section. Therefore, one either has to reference the “Search” function or have previous knowledge of the command in order to use Komodo effectively. Ultimately, Komodo 9 is a more efficient editor than PyCharm, but is held back by an icon-heavy menu.

Saturday, January 31, 2015

4th Grade Girl Python Coder - Tiled Map Creation

As fathers and mothers, we protect our children from disappointment.  In our quest to shield them from failure, we expect too little from them.  Every week, I am amazed by an ordinary 9 year old girl, banging out Python code in PyCharm from a blank screen.  Girl Coder represents one possible future of America.  Although in 20 years, she may be a baker, ballerina, housewife, or teacher, today she is a coder.

For many years, I had under the mistaken impression that kids under age 12 could not learn to program effectively.  I was wrong.  They can do it.  I made many mistakes as a parent-as-teacher with my first child.   The breakthrough insight for me came when I realized that almost all the books and curriculum out there was designed for adults.  At the time, back in 2011, most of the curriculum for children was still based on Java.  The bigger problem was that the curriculum was designed for adults, not children.  

Today, is just another Saturday stay-at-home morning for Girl Coder, age 9.  No surfing today as her brother took off to Tahoe for snowboarding and we decided to relax indoors for a change.  Piano and Python got her attention, not necessarily in that order.  :-)

She built a tile map using Tiled today.  She then used PyCharm to write a Pygame program to move a  girl around a map. This is a modification of PyChildren Lesson 3, The Moving Square.

The first step to make the lesson easier for young children is to use Tiled to output a png file instead of a TMX or JSON file.  In this game, she is using one large image as the entire map.  By using an image instead of JSON or TMX data, we don't have to parse the data.  Girl Coder uses Tiled like a paint program.  She likes the stamps and bucket fills.  Within about 20 minutes, kids can build a pretty snazzy looking map for their games.

The modification to lesson 3 starts off pretty simply.  For this lesson, the girl stays in the center of the screen.  The map moves.   The first tricky part is that she needed to move the map to the left in order to move the girl to the right.   That's not too bad since you can immediately test and see that the girl is moving in the wrong direction and just change things from addition to subtraction.

The goal is to get the girl to appear to move to the right.

In order to do this, the girl remains stationary and the map moves to the left.

In order to move an image to the left, subtract 1 from the x-axis.

At this stage, I'm not sure if she understands the concept of moving the map to the left to get the girl to appear to be moving to the right.  I think it's okay if she doesn't get it.  I'll plan on going through the map lesson again from the beginning and have her implement bounds detection.  She's developing a story with the map.  There are scary places and places with treasure.

The sequence for this lesson.

  1. Blank Screen
  2. Stationary Square
    1. Modify lesson to blit the background map to the screen
  3. Moving Square
    1. Modify lesson to move the map around instead of the player
  4. Keyboard Input
    1. Using the keyboard instead of the touchscreen

At this stage you can stop.  it's cool to see the character move around a map that the child made.  it is somewhat unsettling to not have bounds detection and run out of map.   Since Girl Coder has completed this same drill a number of times, I added bounds detection to the lesson.

Challenge of Bounds Detection

The main challenge with the lesson is how to get the girl to stay on the screen.  To prevent the girl from moving left, it is relatively easy.  Remember, to give the appearance that she's moving left, you're moving the map to the right.  You move things to the right by adding 1 to the x coordinate.  If you name the x coordinate map_x, then you move the character to the right by adding 1 every time through the loop.  

So, what number does map_x need to be less than?  Well, if you started map_x at 0, then when you moved the map to left, you subtracted 1 every time through the loop.  map_x then existed only as a negative number.  As long as map_x is less than zero, you can add one to it.  As soon as the number gets to zero, stop adding numbers to it.

As this is confusing, let's look at the code.

The size of the map is 1216 pixels by 826 pixels. The size of the Pygame window that the game is played in is 480 by 320.  You'll need to help the child with this section.
Here's the entire code listing.

Read Previous Adventures of Girl Coder

Other Options If You Can't Teach Your Own Kids

My daughter also takes classes at in Palo Alto.  The class is great.  It's run by Dr. Mark Miller and Dr. Len Erickson.  There are two levels, grades 1-3 and grades 4-5.  You may wonder if a 2nd grader can code.  Can they even type?  Yes, they can.  

At the beginning of 2015, it's more common to teach children to program.  The curriculum at is great.  It resembles my PyChildren curriculum, though my curriculum is designed for one-to-one teaching.  I'm not sure which method is more effective for teaching, but the PyChildren method is designed to bond your kids, not just to teach them programming. 

Monday, November 3, 2014

Sunday, November 2, 2014

Pygame Virtual Controller Update

I worked with my son for about 2 hours today on the Pygame virtual controller for Android.   The main challenge with the controller is the use of sine, cosine, and tangent.  Although we all learn trigonometry in school, how often do you use it?  Outside of making games, I never use it.

Another challenge is getting comfortable with sprites and sprite groups for the bullets.  Since the bullets are simple, we could easily make the game without sprites.  It's possible to use rectangles stored in lists.  Sprites have a number of advantages over rectangles.  I like to use sprites because its a concise way to organize all the bullets into a single sprite group and then use bullet_group.update() and bullet_group.draw() to manage all the bullets on the screen.

The first time you type in a sprite class, it looks a bit odd.  I think the oddness of the line pygame.sprite.Sprite.__init__(self) makes the sprite more intimidating than it really is.

class Bullet(pygame.sprite.Sprite):
    def __init__(self):
        self.image = pygame.Surface((6,6))
        self.rect = self.image.get_rect()

After getting the bullets to fire properly with sprite groups, the next challenge was to get the player to move around the screen with a secondary virtual controller.  Although we built the code to calculate the angle of the controller for firing in the previous lesson, the player wasn't moving.  Once the player starts moving, the angle needs to be calculated from the center point of the player.  The modification to the code is minimal, but the conceptual leap of thinking of the opposite, adjacent and hypotenuse sides can be daunting when the triangle is moving all around the screen.  

Once you get the angle and the center, the code to move the player is straightforward.

def move(angle, center):
    hypotenuse = 10.0
    adjacent = math.cos(angle) * hypotenuse
    x = int(adjacent + center[0])
    opposite = math.sin(angle) * hypotenuse
    y = int(center[1] - opposite)
    return ((x, y))
At the end of the lesson, he had a working app with 360 degree firing and movement.

The next step is to get this working on his accelerometer game.  We're bumping up into the limitations of single-point touch and are trying to use the accelerometer for movement.  It's easy to access the Android accelerometer, but it's uncertain how playable the game will be.  We're using Cube Runner as a model for playability.

Saturday, November 1, 2014

Dart and StageXL Versus Python and Pygame for Teaching Children

I've used Python, Pygame, and pgs4a for several years.  I've been using Dart and StageXL for less than a month.  So far, I like Dart more than Javascript, Ruby, or Java.  The combination of Dart and StageXL is more friendly than Kivy.

Python and Pygame are completely different from Dart and StageXL.  This is okay with me as I'm focused on teaching children to program.  I'm not concerned about the end product.  The main criteria is what is a good language to teach programming concepts and what will keep their interest.

With this criteria in mind, I'll give my opinion.  Python and Pygame is the easiest path.  As proof of how easy it is to learn, my 9 year daughter can create games with Pygame using the PyCharm IDE and starting with a blank screen.  This is not unusual.  She's also learning Python at school in the 4th grade.  However, she's focused on turtle, not Pygame at school.   At home, she uses Pygame.  She can get through the lessons thanks to the awesome code completion of PyCharm.

My son can build complex apps on the Android phone with Python, Pygame and pgs4a.  He's actually pushing some of the limits of this stack and encountering known bugs.  I don't want to list all the bugs with pgs4a on Android, but from looking at StackOverflow and the questions I get by email, I know that multiple people are having problem with the sound mixer causing slowdown of the main while loop in some circumstances.  There are screen resizing problems on the Moto-G.  The lack of multi-point touch is causing a lot of usability problems for many people.

Although we looked at Kivy to solve some of these problems, I also evaluated Dart as a teaching alternative.  So far, I like it quite a bit.   This StageXL cookbook is quite fun.  Dart also has these cool Polymer.dart and AngularDart pieces.  There's info to get the Dart app running on Android as a web app.  I'm sure all of these will get better.

I'm planning to move to Dart as the basis for future curriculum for my son.  There's some downsides compared to Python.
  • The Dart Editor is pretty cool, but it doesn't do split-screen.  I can't view the same file in two windows at the same time.
  • PyCharm Pro can handle Dart, but it's not as smooth as the Dart Editor
  • The debug info of the Dart Editor is confusing
  • There's less Dart documentation geared for children.   There's a ton of Python information designed specifically for kids
  • Python and Pygame is easier.  
    • You can run everything in a single block of code without any functions or classes.  You can then go back and organize the code into classes when the kid gets it running.
    • You've got to deal with HTML, CSS in addition to Dart
  • The student may spend more of their time with HTML and CSS instead of learning programming concepts.  Tweaking the visual design of the app with HTML and CSS is more accessible and more rewarding than dealing with lists, parsing, and classes.   Designing the interface is not the purpose of these lessons.  The goal is to learn about data structures, classes, methods, functions, types.
  • Using the Python console or iPython is pretty awesome.  
Although I've been going fairly light on design, I think it's time to incorporate more design elements into his games.

There are many advantages to Dart:

  • The optional typing is really nice to isolate errors, especially for teaching purposes.
  • It returns a floating point if you do something like 1/3.  Python 2.7 will return 0.  Python 3.4 will return 0.33333, which is what you expect.  pgs4a will only work with Python 2.7.
  • Dart can be used on the server and the browser.  It also feels natural to do this.
  • Building Python strings with "string_here {}".format(var)  isn't as nice as Dart's "string_here$var"
  • Dart has this quick little "assert" statement to check for errors.
  • The graphics and UI components are pretty awesome on Dart.  With Pygame/pgsa, the only GUI toolkit I got to work was SGC and it was still a bit funky with things like text input on the phone.  My son was starting to waste a lot of time building his own button widgets.   Pygame is really designed for games.  It's not that great with the buttons, menus, text.  It's usable, but I think my son is ready for more UI work
  • The huge advantage to Dart is the distribution mechanism.  The Android apk file produced by pgs4a is big.  While it can be put into the Google Play store, it's a bit of a hassle, so much so that he's never put it into Google Play.  Also, his friends can't play the game on their iPhone, which is still in use by about half the teenagers.  He's still at the stage of only sharing games with friends and family, but I'm hoping that a web app will make it easier.

Fun and fast little exercises.

import 'dart:html' as html;
import 'package:stagexl/stagexl.dart';
import 'dart:math';

void main() {

void makeCanvas(var radius){
  var canvas = html.querySelector('#stage');
  var stage = new Stage(canvas);
  var renderLoop = new RenderLoop();

  List shapes = new List();
  var c_color = Color.Black;
  var rad = int.parse(radius);
  rad = rad * 4;
  print("the radius is $rad");

  for (int i = 50; i < 800; i= i + 50){
    for (int y = 50; y < 600; y = y +50){
      var r = new Random();
      int r_dec = r.nextInt(255);
      var r_g = new Random();
      int g_dec = r_g.nextInt(255);
      var b = new Random();
      int b_dec = b.nextInt(255);
      String a_hex_str = 255.toRadixString(16);
      String r_hex_str = r_dec.toRadixString(16);
      String g_hex_str = g_dec.toRadixString(16);
      String b_hex_str = b_dec.toRadixString(16);
      String col_hex = ('0x$a_hex_str$r_hex_str$g_hex_str$b_hex_str');
      int col = int.parse(col_hex);
      var circ = new Shape();,  y,  rad);;

  for (var my_shape in shapes){

void grabSize(html.MouseEvent event) {
  String the_name = (html.querySelector("#name_box") as html.InputElement).value;
  the_name = the_name.toUpperCase();
  html.querySelector("#name").text = the_name;
  String n_radius = (html.querySelector("#name").text);

Saturday, October 25, 2014

Virtual Controller Angle Tutorial

This is part of an educational curriculum to teach 9th and 10th grade students how to build mobile games on Android. The student needs to be familiar with trigonometry. The primary target student is in 10th grade.
There are two examples. The main lesson is in and focuses on the getting the angle from the virtual controller. The second lesson is in and shows how to fire bullets from a moving player. There is sound generated each time a bullet is fired.
Here's a video snippet showing the 360 degree movement and independent firing.
Screen shot of virtual controller with bullets
Additional sounds can be downloaded from SoundBible.
Since the player is moving, I also implemented a rudimentary bounds detection so that the player doesn't move off the screen.

Create the Controller

In this lesson, the controller is a circle of radius 50. The main objective is to calculate the angle of the player's right thumb in relation to the center of the circle. Since we're running this on a desktop computer before loading it onto an Android phone, the mouse will represent the point the thumb touches the screen., RED,, 50, 2), RED,, 3)
There is a rectangle called, v_control that I'm using with colliderect.
 v_control = pygame.Rect(650, 450, 100, 100)
Before I calculate the angle, I make sure that the thumb is inside of the rectangle for the virtual controller.
if v_control.collidepoint(pos):
    rad = get_angle(pos,

Review Your Trigonometry

You'll need to use arc tangent to calculate the angle in radians. You'll also need to use sine and cosine. If your trigonometry is a rusty, review it now.
math.atanmath.sin, and math.cos are in the python math standard library. You'll need to addimport math at the top of your program.
Review of sine, cosine, and tangent
To use arc tangent you'll need to calculate the lengths of the opposite and adjacent sides of a right triangle. Since the formulas to calculate the lengths of the sides of a triangle are slightly different depending on where the thumb is on the controller, I've divided the controller into four quadrants, starting with quadrant one in the upper right and rotating counter-clockwise.
For each quadrant, you'll need to adjust the formula to calculate the opposite and adjacent sides of the triangle. For example, if the mouse is above the center of the controller, you'll need to subtract the mouse y position from the centery of the controller.

Define Each Quadrant

Diagram of characteristics of each quadrant
For the y-axis, the mouse point is either:
  1. above the center of the controller
  2. below the center of the controller
  3. at the same height of the center of the controller

Quandrants 1 and 2

Mouse Point Located Above Controller Center
If the mouse point is above the center of the controller, than check for one of three conditions:
  1. x is to the right of the controller
  2. x is to the left of the controller
  3. x is at the same point as the centerx of the controller

Quadrant 1

Mouse point is located above and to the right of controller
Diagram of Quadrant 1
Example code. Note that you need to convert to floating point.
center is a two number tuple (400,300), the center of the player. x, y is the mouse position.
    opposite = float(center[1] - y)
    if x > center[0]:
        adjacent = float(x - center[0])
        rad = math.atan(opposite/adjacent)
Here's what it looks like with the game running. Note that the angle of the mouse pointer relative to the center of the virtual controller is the same as the angle of the beam relative to the center of the player.
Screenshot of game with beam in quadrant 1

Quadrant 3

Mouse point is below and to the left of the controller center
If the mouse pointer is not in quadrant 1, add the appropriate radian value. For example, if the mouse pointer is in quadrant 3, then add pi (3.14) to the radian value.
calculation of quadrant 3

Using Radian Angle to Control Beam

Creating a beam is easier than a bullet. It is a line with the starting point at the center of the player and the end point 30 pixels out from the center.  In the next lesson, the beam becomes the gun turret.  I increased the width of the line to 6 pixels.  The end point of the gun turret will become the starting point of the bullet.  
Once you have the angle, use sine and cosine to calculate the length of opposite and adjacent sides of the triangle.
def beam(angle, center):
    :param angle: radians calculated from the virtual controller
    :return: x,y coordinates of the end-point
    Start with the center of the player.  The end of the beam is 100 pixels
    away from the center.  To make a bullet instead of beam, create a class
    for bullet and have the hypoteneuse be an attribute that increases
    in size.  Remember to delete the bullet from the sprite group or list
    when it goes off the screen.
    hypoteneuse = 30.0
    adjacent = math.cos(angle) * hypoteneuse
    x = adjacent + center[0]
    opposite = math.sin(angle) * hypoteneuse
    y = center[1] - opposite
    beam_end = (x, y)
    return beam_end

Shoot Bullets Instead of a Beam

If you want to shoot bullets, I'm using sprites. Don't be intimidated by sprites even though the code looks a bit funky. The bullet moves forward by increasing the length of the hypotenuse by 5 pixels.
class Bullet(pygame.sprite.Sprite):
    def __init__(self, angle, p_pos):
        YELLOW = (250, 223, 65)
        RED = (200, 10, 10)
        self.image = pygame.Surface((6,6)), YELLOW, (3, 3), 3), RED, (3,3), 1)
        self.rect = self.image.get_rect()
        self.hypotenuse = 30.0
        self.angle = angle
        self.cent = p_pos

    def update(self):
        adjacent = math.cos(self.angle) * self.hypotenuse
        x = adjacent + self.cent[0]
        opposite = math.sin(self.angle) * self.hypotenuse
        y = self.cent[1] - opposite = (x, y)
        self.hypotenuse += 5

You'll need to set up a timer for the creation of new bullets so that the bullets don't clump together in a mass of destruction every time you press the fire button.  See the code in for an example in how to create the delay between bullet creation.

Move The Player

In the second example, I'm using almost the same code to move the player around the screen.
Move on to the second lesson on virtual controller angle tutorial.

More games with Python, Pygame, and pgs4a written by a boy in middle school and high school are available for reference to see what a typical child is doing.  It's important to understand that the examples don't show the best way to do things.  They just show a way that a child is getting stuff done. One of the problems I've found with most tutorials is that the examples are best-practice perfect for adults.  I have a theory that children also learn by thinking about how to improve on another child's code.  Additional examples are available
The most likely scenario is to start with Swarm and build from there.
My son is planning to try something with the Android accelerometer.