writeUpProject9.txt

h1. Final Project - VGA Space Game Framework

h3. Problem description

We set out to design a circuit to drive a VGA monitor, then use that circuit to
create a game, which we originally intended to be Tetris-like.

h3. Design 

Our VGA component uses a 25 MHz clock, which we got by halving the 50 MHz clock
on the board by watching the first bit of a counter incremented on the 50 MHz
clock. The clock speed was very important to allow our state machine to sync
with the actual screen updating for things like the vertical and horizontal
sync signals. As a design choice we kept all of the color enabling and setting
signals in the top level and out of the VGA component.

Our game design started by setting up a border and a grid of blocks so that we 
didn't always have to be dealing directly with pixels. Our grid of blocks is 
defined by a 2D array of 12 bit vectors, 4 bits for each of red, green, and blue.
We have a process sensitive to each pixel (column, row) that assigns the color
output signals to the appropriate bits of the matching block. Our game state 
machine then only had to keep track of a pair of integers to track a block in
the grid.

We track an active block and allow the user to move it left, right, and up using
button presses on the board. We also move the active block down at a constant 
rate (gravity), and our state machine takes care of undrawing the previous block 
and identifying the case where the block being moved to is not black, which we 
distinguish by drawing the active block a different color for a collision. This
framework could be extended to implement a Tetris-like game, but we went in a 
different direction.

We implemented a pseudo-random vector with the same number of bits as the
block width of the screen using a feedback polynomial implementation from one of
our previous projects. This runs continually and we sample it every time the 
player falls, when we move the entire map down one and populate the top row with
blocks matching the random vector. The density of the random vector can be
adjusted by changing the constant polynomial. Though we didn't complete a full
game, our design is extendable to any number of games, including a rocket game
where collisions cause hull damage and the speed of the falling effect can
increase periodically. The lose condition could be falling into the bottom row
or taking too much hull damage. The possibilities are endless.

h3. Test your circuit. Include a video

Can you do this Ryan?

h3. Description, and pictures, of any extensions

Did we do any extensions?