Tag Archives: how-to

Recreate Q*bert’s cube-hopping action | Wireframe #42

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Code the mechanics of an eighties arcade hit in Python and Pygame Zero. Mark Vanstone shows you how

Players must change the colour of every cube to complete the level.

Late in 1982, a funny little orange character with a big nose landed in arcades. The titular Q*bert’s task was to jump around a network of cubes arranged in a pyramid formation, changing the colours of each as they went. Once the cubes were all the same colour, it was on to the next level; to make things more interesting, there were enemies like Coily the snake, and objects which helped Q*bert: some froze enemies in their tracks, while floating discs provided a lift back to the top of the stage.

Q*bert was designed by Warren Davis and Jeff Lee at the American company Gottlieb, and soon became such a smash hit that, the following year, it was already being ported to most of the home computer platforms available at the time. New versions and remakes continued to appear for years afterwards, with a mobile phone version appearing in 2003. Q*bert was by far Gottlieb’s most popular game, and after several changes in company ownership, the firm is now part of Sony’s catalogue – Q*bert’s main character even made its way into the 2015 film, Pixels.

Q*bert uses isometric-style graphics to draw a pseudo-3D display – something we can easily replicate in Pygame Zero by using a single cube graphic with which we make a pyramid of Actor objects. Starting with seven cubes on the bottom row, we can create a simple double loop to create the pile of cubes. Our Q*bert character will be another Actor object which we’ll position at the top of the pile to start. The game screen can then be displayed in the draw() function by looping through our 28 cube Actors and then drawing Q*bert.

Our homage to Q*bert. Try not to fall into the terrifying void.

We need to detect player input, and for this we use the built-in keyboard object and check the cursor keys in our update() function. We need to make Q*bert move from cube to cube so we can move the Actor 32 pixels on the x-axis and 48 pixels on the y-axis. If we do this in steps of 2 for x and 3 for y, we will have Q*bert on the next cube in 16 steps. We can also change his image to point in the right direction depending on the key pressed in our jump() function. If we use this linear movement in our move() function, we’ll see the Actor go in a straight line to the next block. To add a bit of bounce to Q*bert’s movement, we add or subtract (depending on the direction) the values in the bounce[] list. This will make a bit more of a curved movement to the animation.

Now that we have our long-nosed friend jumping around, we need to check where he’s landing. We can loop through the cube positions and check whether Q*bert is over each one. If he is, then we change the image of the cube to one with a yellow top. If we don’t detect a cube under Q*bert, then the critter’s jumped off the pyramid, and the game’s over. We can then do a quick loop through all the cube Actors, and if they’ve all been changed, then the player has completed the level. So those are the basic mechanics of jumping around on a pyramid of cubes. We just need some snakes and other baddies to annoy Q*bert – but we’ll leave those for you to add. Good luck!

Here’s Mark’s code for a Q*bert-style, cube-hopping platform game. To get it running on your system, you’ll need to install Pygame Zero. And to download the full code and assets, head here.

Get your copy of Wireframe issue 42

You can read more features like this one in Wireframe issue 42, available directly from Raspberry Pi Press — we deliver worldwide.

And if you’d like a handy digital version of the magazine, you can also download issue 42 for free in PDF format.

Make sure to follow Wireframe on Twitter and Facebook for updates and exclusive offers and giveaways. Subscribe on the Wireframe website to save up to 49% compared to newsstand pricing!

The post Recreate Q*bert’s cube-hopping action | Wireframe #42 appeared first on Raspberry Pi.

Convert an ATX computer supply to a bench power supply

via Dangerous Prototypes

Using an old computer ATX power supply as a high-performance workbench power supply @ DroneBot Workshop:

A Bench Power Supply is an essential component for any serious electronics experimenter. But a good supply with multiple output voltages and a high current capability can set you back some serious cash. In this article we’ll look at an alternative – using an old computer ATX power supply as a high-performance workbench power supply. It’s a simple project that can give you a highly capable piece of equipment for next to nothing

Check out the video after the break.

Recreate Time Pilot’s free-scrolling action | Wireframe #41

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Fly through the clouds in our re-creation of Konami’s classic 1980s shooter. Mark Vanstone has the code

Arguably one of Konami’s most successful titles, Time Pilot burst into arcades in 1982. Yoshiki Okamoto worked on it secretly, and it proved so successful that a sequel soon followed. In the original, the player flew through five eras, from 1910, 1940, 1970, 1982, and then to the far future: 2001. Aircraft start as biplanes and progress to become UFOs, naturally, by the last level.

Players also rescue other pilots by picking them up as they parachute from their aircraft. The player’s plane stays in the centre of the screen while other game objects move around it. The clouds that give the impression of movement have a parallax style to them, some moving faster than others, offering an illusion of depth.

To make our own version with Pygame Zero, we need eight frames of player aircraft images – one for each direction it can fly. After we create a player Actor object, we can get input from the cursor keys and change the direction the aircraft is pointing with a variable which will be set from zero to 7, zero being the up direction. Before we draw the player to the screen, we set the image of the Actor to the stem image name, plus whatever that direction variable is at the time. That will give us a rotating aircraft.

To provide a sense of movement, we add clouds. We can make a set of random clouds on the screen and move them in the opposite direction to the player aircraft. As we only have eight directions, we can use a lookup table to change the x and y coordinates rather than calculating movement values. When they go off the screen, we can make them reappear on the other side so that we end up with an ‘infinite’ playing area. Add a level variable to the clouds, and we can move them at different speeds on each update() call, producing the parallax effect. Then we need enemies. They will need the same eight frames to move in all directions. For this sample, we will just make one biplane, but more could be made and added.

Our Python homage to Konami’s arcade classic.

To get the enemy plane to fly towards the player, we need a little maths. We use the math.atan2() function to work out the angle between the enemy and the player. We convert that to a direction which we set in the enemy Actor object, and set its image and movement according to that direction variable. We should now have the enemy swooping around the player, but we will also need some bullets. When we create bullets, we need to put them in a list so that we can update each one individually in our update(). When the player hits the fire button, we just need to make a new bullet Actor and append it to the bullets list. We give it a direction (the same as the player Actor) and send it on its way, updating its position in the same way as we have done with the other game objects.

The last thing is to detect bullet hits. We do a quick point collision check and if there’s a match, we create an explosion Actor and respawn the enemy somewhere else. For this sample, we haven’t got any housekeeping code to remove old bullet Actors, which ought to be done if you don’t want the list to get really long, but that’s about all you need: you have yourself a Time Pilot clone!

Here’s Mark’s code for a Time Pilot-style free-scrolling shooter. To get it running on your system, you’ll need to install Pygame Zero. And to download the full code and assets, head here.

Get your copy of Wireframe issue 41

You can read more features like this one in Wireframe issue 41, available directly from Raspberry Pi Press — we deliver worldwide.

And if you’d like a handy digital version of the magazine, you can also download issue 41 for free in PDF format.

Make sure to follow Wireframe on Twitter and Facebook for updates and exclusive offers and giveaways. Subscribe on the Wireframe website to save up to 49% compared to newsstand pricing!

The post Recreate Time Pilot’s free-scrolling action | Wireframe #41 appeared first on Raspberry Pi.

Code Jetpac’s rocket building action | Wireframe #40

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Pick up parts of a spaceship, fuel it up, and take off in Mark Vanstone’s Python and Pygame Zero rendition of a ZX Spectrum classic

The original Jetpac, in all its 8-bit ZX Spectrum glory

For ZX Spectrum owners, there was something special about waiting for a game to load, with the sound of zeros and ones screeching from the cassette tape player next to the computer. When the loading screen – an image of an astronaut and Ultimate Play the Game’s logo – appeared, you knew the wait was going to be worthwhile. Created by brothers Chris and Tim Stamper in 1983, Jetpac was one of the first hits for their studio, Ultimate Play the Game. The game features the hapless astronaut Jetman, who must build and fuel a rocket from the parts dotted around the screen, all the while avoiding or shooting swarms of deadly aliens.

This month’s code snippet will provide the mechanics of collecting the ship parts and fuel to get Jetman’s spaceship to take off.  We can use the in-built Pygame Zero Actor objects for all the screen elements and the Actor collision routines to deal with gravity and picking up items. To start, we need to initialise our Actors. We’ll need our Jetman, the ground, some platforms, the three parts of the rocket, some fire for the rocket engines, and a fuel container. The way each Actor behaves will be determined by a set of lists. We have a list for objects with gravity, objects that are drawn each frame, a list of platforms, a list of collision objects, and the list of items that can be picked up.

Jetman jumps inside the rocket and is away. Hurrah!

Our draw() function is straightforward as it loops through the list of items in the draw list and then has a couple of conditional elements being drawn after. The update() function is where all the action happens: we check for keyboard input to move Jetman around, apply gravity to all the items on the gravity list, check for collisions with the platform list, pick up the next item if Jetman is touching it, apply any thrust to Jetman, and move any items that Jetman is holding to move with him. When that’s all done, we can check if refuelling levels have reached the point where Jetman can enter the rocket and blast off.

If you look at the helper functions checkCollisions() and checkTouching(), you’ll see that they use different methods of collision detection, the first being checking for a collision with a specified point so we can detect collisions with the top or bottom of an actor, and the touching collision is a rectangle or bounding box collision, so that if the bounding box of two Actors intersect, a collision is registered. The other helper function applyGravity() makes everything on the gravity list fall downward until the base of the Actor hits something on the collide list.

So that’s about it: assemble a rocket, fill it with fuel, and lift off. The only thing that needs adding is a load of pesky aliens and a way to zap them with a laser gun.

Here’s Mark’s Jetpac code. To get it running on your system, you’ll need to install Pygame Zero. And to download the full code and assets, head here.

Get your copy of Wireframe issue 40

You can read more features like this one in Wireframe issue 40, available directly from Raspberry Pi Press — we deliver worldwide.

And if you’d like a handy digital version of the magazine, you can also download issue 40 for free in PDF format.

Make sure to follow Wireframe on Twitter and Facebook for updates and exclusive offers and giveaways. Subscribe on the Wireframe website to save up to 49% compared to newsstand pricing!

The post Code Jetpac’s rocket building action | Wireframe #40 appeared first on Raspberry Pi.

How to correctly set the motor current limit on an A4988 stepper motor driver

via Dangerous Prototypes

Michael posted detailed instructions of how to set up your A4988 stepper motor driver’s motor current limit:

One important thing to set up when using these drivers is the motor current limit. This is especially important when you’re using a higher input voltage than what the motor is rated for. Using a higher voltage generally enables you to get more torque and a faster step speed, but you’ll need to actively limit the amount of current flowing through the motor coils so that you don’t burn your motor out.

See the full post at the-diy-life.com.

Check out the video after the break.

Using modular synth to control Atem camera switching over WiFi using ESP8266

via Dangerous Prototypes

Sebastian writes:

I’ve been wanting to control my camera switching from my modular synth. So I made a setup where a low to high transition on a digital input on an ESP8266 module generates an OSC message on the WiFi network for the ATEM Mini Pro switcher to change cameras. Here, it’s triggered from the kick but it could be any clock, gate or trigger signal. Makes use of atemOSC.

More details on Little-Scale blog.

Check out the video after the break.