Andrew Richards, September 2015.

8 rows of 8 LEDs, teensy joystick... I found Snake as mentioned in the blurb for the AstroPi, but no Tetris. So here's TetriPiSense, my motivation for getting to grips with my Sense Hat... and indeed GitHub too.

The program uses the sense_hat and pygame libraries to provide much of the underlying functionality. The Sense Hat joystick is mapped to keyboard keys, so for the Unicorn Hat (with no joystick), this program should still work - just use your keyboard's arrow keys (also Esc key to quit).

You'll need the pygame and sense_hat libraries installed on your Pi. pygame is probably already installed - if not you'd look for the package name pygame or python-pygame - for example on Debian-flavoured Linux one of (for Python 2, Python 3 resp.),

sudo apt-get install python-pygame
sudo apt-get install python3-pygame

and if you've not already installed the sense_hat library, one of,

sudo apt-get install python-sense-hat
sudo apt-get install python3-sense-hat

Lots of other ways of installing Python packages instead, such as pip,

pip install pygame
pip install sense-hat

Now tetripisense.py just needs to be placed somewhere you / your system can find it, see below for usage.

If you're directly connected (keyboard, mouse, monitor) to the Raspberry Pi with Sense Hat, you should be able to launch the game like this (although writing with Python 3 in mind, Python 2.7 seems to work fine too, I don't know about earlier versions of Python),

python tetripisense.py

The joystick controls the block: Move left/right, rotate (clockwise), drop the current block; all of these are also available via the keyboard (USB-connected to Pi) using the equivalent arrow keys, as well as the Esc key to exit the game.

If you're accessing the Raspberry Pi remotely (e.g. via ssh),

export DISPLAY=0:0; sudo python tetripisense.py

Note that this runs the program with full administrator privileges, and makes your Raspberry Pi system much more exposed and vulnerable to anything dodgy that the game might try to do to your Pi. Note that the [ssh] keyboard doesn't control the game when you're connected like this (although Ctrl-C will quit).

See below if you'd like the program to startup when your Pi starts.

Original PiLite implementation: Stephen Blythe
This Sense Hat implementation: Andrew Richards

http://free.acrconsulting.co.uk/other/tetripisense.html

Gnu General Public License, version 3 and above: Please see the included LICENSE file.

Rotation: Please see TODO.md: Rotation uses pygame and rotates around an axis of the top-left of the shape. This is mostly fine, but for a long narrow block, rotating around the centre of the block might look a bit more polished.

Possible starting points were Tetromino written by Al Sweigart included within Raspbian, and Stephen Blythe's implementation for Ciseco's PiLite. I chose to adapt the latter since it was aimed at a similar grid-of-LEDs display so should map well to the Hat - indeed, my initial hacks to get it working on the Sense Hat didn't require much work, although I did then spend a fair amount of time polishing the code and ironing out a few bugs.

Having only 8 vertical LEDs makes it harder to achieve a reasonably playable game, so I added extra 'virtual' rows of pixels for the behind-the-scenes pygame.Surface, which gives the sense of the new block emerging at the top of the display, rather than the whole block suddenly appearing at the top of the display - this gives the player a bit more time to manoevre the new block and results in the game feeling a bit more polished.

I've tried to move some chunks of code into functions where possible to make the logic clearer; unfortunately the main game loop still contains quite a lot of code but is hopefully reasonably straightforward. Most of the manipulation of the falling block and the background is done with pygame functions; actually displaying the game uses the sensehat_display() function which converts from the pygame representation of the display to the representation used by sense_hat's set_pixels() method.

Unit or other tests are conspicuously absent here but would be very worthwhile, even if only part of the code lends itself to this.

It's fun to have the Pi run this game on its own without a mouse, keyboard, screen - a sort of minimal handheld games console, powered by an external battery, such as the now fairly widely available external battery packs for phones that provide power via USB cables.

To do this, the Pi will need to respond to the Hat's joystick when it starts up. Given this is mapped to the keyboard, just add run_game.py to the Pi's customisable startup script to wait for the joystick button (mapped to the Return key) to be pressed (in fact any keypress, so moving the joystick works too): Add the following line before the final exit 0 line in /etc/rc.local,

python /home/pi/tetripisense/run_game.py

assuming run_game.py and tetripisense.py are in the directory above. When you finish playing you can shutdown the Pi cleanly by turning it upside down briefly which will initiate a shutdown: The SenseHat's accelerometer is checked to see if the Hat is upside-down and calls shutdown if so - but only during the Press joystick (run_game.py) loop, not during games.

Note that this approach will run run_game.py and tetripisense.py with administrator privileges which is poor practice.