GAMES

[ MAKE GAMES WITH PYTHON ]
The first thing we do on
each loop of our game
is set three variables...
only three methods and a range of variables to affect and track each
bullet: move, draw, and loadImages. How do the bullets know when they
are hitting something? Because each bullet created in our game is stored
in the bullets list in each of our ships, we use the ships class method
checkForHit to see whether or not any of the bullets hit anything.
There’s no real reason for doing it this way - we could have each bullet be
responsible for checking if it hit something - but it does make sense to
have each ship keep an eye on whether the bullets it fired hit something.
Game events
Now we know what each file is responsible for in our latest game, we can
start walking through how they all come together. As soon as our game
is run, the global variables are set and all of the imports between lines
1 and 39 are applied. Let’s take a look at our main loop starting on line
90 in aliens.py. The first thing we do on each of our game loops is to set
three variables: timeTicks, mousePosition, and mouseStates. The
timeTicks variable keeps track of how many milliseconds have passed
since we started the game. We can use this to set variables or create
new objects after a set amount of time, as we do on line 128, where we
create a new enemy ship after every 1.5 seconds of the game playing.
mousePosition is where we store the position of the mouse in our game
window. Remember, our mouse position is relative to the top-left of our
Pygame window. We use the mouse to move our ship around in our game,
so we need to keep a constant track of where our mouse is; storing our
mousePosition at the start of each loop saves us a little time and typing
if we need to check the position more than once every loop. mouseStates
is where we save the ‘state’ of our mouse buttons, namely which buttons
are being pressed down and which ones aren’t. We use the left mouse
button to fire our weapons and start our game so having that information
stored globally means we can check against one variable rather than
calling pygame.mouse.get_pressed() multiple times.
[ The Aliens are trying to kill me ]
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