Add a README describing steps to write a Tetris game

Author: lordmauve

README.md

@@ -1 +1,92 @@
-# tetris
+# London Python Dojo - Tetris
+
+The task for tonight is to create a clone of Tetris. This page lays out some
+of the decisions and tasks.
+
+This is an aid to coordinating as a remote team.
+
+
+# Game engine
+
+You will need to decide on a 2D game framework. Some candidates are:
+
+* [Pygame Zero](https://pygame-zero.readthedocs.io/en/stable/)
+* [Wasabi2D](https://wasabi2d.readthedocs.io/en/latest/)
+* [Arcade](https://arcade.academy/)
+* [PursuedPyBear](https://ppb.dev/)
+* [ursina](https://www.ursinaengine.org/)
+
+I would not recommend these for this project:
+
+* [Pygame](https://www.pygame.org/news) - you will have to write a game loop
+  and event handling yourself before beginning.
+* [Pyglet](https://pyglet.readthedocs.io/en/latest/) - being lower-level to
+  OpenGL, this does not have a simple API for polygon/rectangle drawing, only
+  sprites and text.
+
+
+# Tasks
+
+The following tasks are split up according to a "Model-View-Controller"
+pattern to make it easier to visualise the dependencies between the tasks,
+but this is not the only way (and may not be the best way) to write the game.
+
+
+## Model
+
+1. Describe the seven tetronimo pieces (as
+   [described here](https://tetris.fandom.com/wiki/Tetromino)).
+1. Generate a random piece. Show the next piece that will be generated.
+1. Rotate a tetronimo. This requires a centre of rotation for each tetronimo.
+   See [here for a description of this in the official games](https://strategywiki.org/wiki/Tetris/Rotation_systems).
+1. Model the grid of filled cells.
+1. Allow testing whether a tetronimo intersects filled cells at a given
+   position.
+1. Write a tetronimo into the filled cells.
+1. Remove each line that is filled and collapse lines above.
+1. Keep score.
+
+
+## View
+
+1. Create a game window.
+1. Draw the boundary of the play area.
+1. Draw the filled cells.
+1. Draw the active tetronimo.
+1. Draw the next tetronimo to drop.
+1. Animate the removal of a line.
+1. Show the score.
+1. Allow drawing "game over" over the screen.
+
+
+## Controller
+
+1. At the start of the game, make the next tetronimo the active tetronimo.
+1. Drop one step every *t* seconds. If the tetronimo cannot occupy the space
+   below it, write it into the filled cells. Trigger an animation if a line is
+   filled. Then make the next tetronimo active.
+1. Add keys for left/right. These do nothing if there is no space for the
+   tetronimo.
+1. Add keys for rotate clockwise/anticlockwise. These do nothing if there is
+   no space for the rotated tetronimo. At the walls, tetronimos may be moved
+   outwards to accomodate the rotation.
+1. If there is no room to introduce the active piece, show game over.
+1. On the game over screen, press a key to restart.
+1. Implement the "drop all the way" operation.
+
+
+## Publication
+
+1. Describe requirements in a requirements.txt
+1. Write a README.
+
+
+## Stretch goals
+
+1. Animate the rotation of the pieces.
+1. Animate the drop operation(s).
+1. Make the game speed increase very slowly (logarithmically?)
+1. Add [juice](https://youtu.be/Fy0aCDmgnxg) - screen shake, trails, particles,
+   sound effects.
+1. Add a title screen.
+1. Publish to PyPI.