9.4: The Usual Setup Code
- Page ID
- 13614
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)# Squirrel Eat Squirrel (a 2D Katamari Damacy clone) # By Al Sweigart al@inventwithpython.com # http://inventwithpython.com/pygame # Released under a "Simplified BSD" license import random, sys, time, math, pygame from pygame.locals import * FPS = 30 # frames per second to update the screen WINWIDTH = 640 # width of the program's window, in pixels WINHEIGHT = 480 # height in pixels HALF_WINWIDTH = int(WINWIDTH / 2) HALF_WINHEIGHT = int(WINHEIGHT / 2) GRASSCOLOR = (24, 255, 0) WHITE = (255, 255, 255) RED = (255, 0, 0) CAMERASLACK = 90 # how far from the center the squirrel moves before moving the camera MOVERATE = 9 # how fast the player moves BOUNCERATE = 6 # how fast the player bounces (large is slower) BOUNCEHEIGHT = 30 # how high the player bounces STARTSIZE = 25 # how big the player starts off WINSIZE = 300 # how big the player needs to be to win INVULNTIME = 2 # how long the player is invulnerable after being hit in seconds GAMEOVERTIME = 4 # how long the "game over" text stays on the screen in seconds MAXHEALTH = 3 # how much health the player starts with NUMGRASS = 80 # number of grass objects in the active area NUMSQUIRRELS = 30 # number of squirrels in the active area SQUIRRELMINSPEED = 3 # slowest squirrel speed SQUIRRELMAXSPEED = 7 # fastest squirrel speed DIRCHANGEFREQ = 2 # % chance of direction change per frame LEFT = 'left' RIGHT = 'right'
The start of the program assigns several constant variables. This program frequently makes use of the half length of the width and height of the window so much that the HALF_WINWIDTH and HALF_WINHEIGHT variables store these numbers.
The "camera slack" is described later. Basically, it means that the camera will begin following the player squirrel when it moves 90 pixels away from the center of the window.
The comments next to these constants explains what the constant variable is used for.