optimization of a windows batch file arcade game - windows

Question

I made a batch file game, and it works, but it is choppy and ugly. I already know about threading, but I don't want to implement that in my first version. I am hoping to have the optimization down before I start doing more advanced things with this game. my question is this: What optimizations can I make to this game, so that it will 1. not be choppy and 2. not be quite so annoying in the display. any ideas or comments about how to make it faster clearer or take less memory are welcome, however, please do not post answers like: "don't use batch" "rewrite it in (insert language here)" "do this part with vb-script" etc... as they are not helpful, nor do they answer the question. any and all non batch hating criticism is welcomed.
here is the code:
#setlocal enableextensions enabledelayedexpansion
#echo off
color 0a
mode con lines=35 cols=50
cls
set instructions=use a and d to move left and right, w to fire. use q to quit and p to pause.
set height=30
set length=
set screen=50
set swidth=20
set amo=8
set lives=3
set 1=0
set 2=1
set 3=2
set 4=3
set 5=4
set 6=0
set 7=1
set 8=2
set 9=3
set 10=4
echo. What quality would you like?
echo. 1. fast, but the graphics suck!
echo. 2. medium both ways.
echo. 3. slow, but the graphics are better!
choice /n /c:123
set firequal=%errorlevel%00
cls
echo %instructions%
echo.
pause
cls
::main
:controls
cls
if %height% EQU 2 goto gameover
if %lives% LSS 1 goto gameover
cls
set /a shouldbomb+=1
set /a whenbomb=shouldbomb%%15
if %whenbomb% == 9 call :bomb
if '%ret%'=='1' exit /b
set ret=
cls
set alive=
for /l %%i in (1,1,10) do if defined %%i set alive=true
if not defined alive goto win
cls
for /l %%i in (1,1,5) do (
if defined %%i (
set /p a=[_] <nul
) else (
set /p a=... <nul
)
)
echo.
for /l %%i in (6,1,10) do (
if defined %%i (
set /p a=[_] <nul
) else (
set /p a=... <nul
)
)
for /l %%a in (1,1,%height%) do echo.
echo %length%[]
echo.
for /l %%i in (1,1,%amo%) do set /p a=^|<nul
echo.
choice /c adwqp0 /n /t 1 /d 0
if %errorlevel% equ 1 goto :left
if %errorlevel% equ 2 goto :right
if %errorlevel% equ 3 goto :fire
if %errorlevel% equ 4 (cls&exit /b)
if %errorlevel% equ 5 pause&goto controls
if %errorlevel% equ 6 goto :inactive
goto controls
::move player left
:left
if '!length!' NEQ '' set length=!length:~0,-1!
goto controls
::move player right
:right
call :strlen shiplen length
if %shiplen% GTR %swidth% goto controls
set length=%length%
goto controls
::fire a shot upwards
:fire
if '!amo!' LSS '1' goto controls
cls
set /a amo-=1
for /l %%i in (%height%,-1,2) do (
cls
for /l %%i in (1,1,5) do (
if defined %%i (
set /p a=[_] <nul
) else (
set /p a=... <nul
)
)
echo.
for /l %%i in (6,1,10) do (
if defined %%i (
set /p a=[_] <nul
) else (
set /p a=... <nul
)
)
for /l %%j in (1,1,%%i) do echo.
echo %length% ^
set /a ship=height-%%i-1
for /l %%b in (1,1,!ship!) do echo.
echo %length%[]
echo.
for /l %%i in (1,1,%amo%) do set /p a=^|<nul
echo.
for /l %%a in (1,1,%firequal%) do call >nul 2>&1
)
call :checkshot
set /a shouldbomb+=1
set /a whenbomb=shouldbomb%%2
if %whenbomb% == 0 call :bomb
goto controls
:inactive
if %amo% LSS 10 set /a amo+=1
if !height! NEQ 2 set /a height-=1
call :bomb
goto controls
:bomb
:btop
set bombx=
for /l %%a in (1,1,10) do (
if defined %%a (
set /a randomnum=%random%%%5
if '!%%a!'=='%randomnum%' (
set /a "bombx=5*(!%%a!)"
)
)
)
)
if not defined bombx goto btop
cls
set bomb=
for /l %%b in (1,1,!bombx!) do (
set bomb=!bomb!
)
set /a bombh=height-1
for /l %%c in (1,1,!bombh!) do (
cls
for /l %%i in (1,1,5) do (
if defined %%i (
set /p a=[_] <nul
) else (
set /p a=... <nul
)
)
echo.
for /l %%i in (6,1,10) do (
if defined %%i (
set /p a=[_] <nul
) else (
set /p a=... <nul
)
)
for /l %%b in (1,1,%%c) do echo.
echo !bomb!x
set /a ship=height-%%c-1
for /l %%b in (1,1,!ship!) do echo.
echo %length%[]
echo.
for /l %%i in (1,1,%amo%) do set /p a=^|<nul
echo.
for /l %%a in (1,1,%firequal%) do call >nul 2>&1
)
if "%bomb%" == "%length%" call :looselife
if "%bomb% " == "%length%" call :looselife
if "%bomb%" == "%length% " call :looselife
if "%bomb% " == "%length%" call :looselife
if "%bomb%" == "%length% " call :looselife
exit /b
:strlen <resultVar> <stringVar>
(
setlocal EnableDelayedExpansion
set "s=!%~2!#"
set "len=0"
for %%P in (1024 512 256 128 64 32 16 8 4 2 1) do (
if "!s:~%%P,1!" NEQ "" (
set /a "len+=%%P"
set "s=!s:~%%P!"
)
)
)
(
endlocal
set "%~1=%len%"
exit /b
)
:checkshot
call :strlen slen length
for /l %%i in (0,5,20) do (
if '!slen!' == '%%i' (
set /a hit=%%i
set /a hit=hit/5+1
set /a hit2=hit+5
if not defined !hit2! set !hit!=
if defined !hit2! set !hit2!=
)
)
exit /b
:looselife
set /a lives-=1
set length=
set 1=0
set 2=1
set 3=2
set 4=3
set 5=4
if %lives% GTR 1 timeout /nobreak 1 >nul 2>&1
exit /b
:win
cls
echo YOU WIN^!^!^!^!
echo.
echo GOOD JOB^!^!^!
echo.
pause
cls
exit /b
:gameover
cls
echo YOU LOOSE.
echo.
echo PLEASE TRY AGAIN.
echo.
pause
cls
set ret=1
thank you in advance for any help.
P.S. I am writing this game to convince a friend to learn something besides html, and while batch isn't the best, he uses windows, and he will only do something simple for now. He is twelve, so I think batch is best option.

Answer 1

You can definitely improve things considerably. I know, because I have already produced a very smooth and playable version of SNAKE using pure Windows batch! Give it a try - I think you will be surprised and impressed with what musty old batch can do :-)
Of course the link has the code, but it also has pointers on some of the techniques I used to make the came perform so well. Read the entire first post carefully, and read the remainder of the thread for some additional important developments.
Optimization is a large topic. Rather than repeat all the information here, I will simply summarize. Follow the link for more details.
1) Minimize GOTO and CALL statements.
For major speed improvements over traditional batch function calls, we developed batch macros with arguments at DosTips. That first macro link develops a number of important concepts. However, the macro form I actually used in the game uses a more elegant solution with arguments appended.
A GOTO loop can be replaced by an infinite FOR loop that runs in a new process. You break out of the loop by EXITing the child process.
2) Greatly improve key press detection in a non-blocking way.
A major limitation of batch is the inability to easily detect a keypress without blocking progress of the game. The problem can be solved by using two processes, both running in the same console window. The controller process reads keypresses and sends them to the main game process via a text file. The controller has multiple modes of operation. The game process sends commands to the controller via another text file. This technique requires careful coordination of input and output redirection.
The CHOICE command is not available on XP. Some folks at DosTips discovered how to use XCOPY to simulate most of the features of CHOICE, and it works on all versions of Windows. Very cool!
3) Screen painting
Building the screen character by character is extremely slow. It is much faster to build the initial screen once, using an "array" of strings with fixed length. Each character within a string represents one "pixel". The position within a string represents the X coordinate, and the string row number represents the Y coordinate. Generally, only a few pixels change for any given screen refresh. Pixels can be "plotted" by using SET with simple substring operations. The entire screen can then be quickly refreshed using CLS followed by ECHO of each line in the screen array.
4) Smooth animation
The amount of work required to perform game logic and screen plotting can vary significantly depending on the current game context. But you want the animation to be smooth. Rather than have a fixed delay between each round of movement, you can instead measure the time since the screen was last updated. Only continue when a pre-determined amount of time has elapsed. As long as all game logic and plotting can occur within the delay time period, then the animation will always be smooth.
Here is pseudo code that describes the timing logic:
initialize delayTime
initialize previousTime
loop (
get currentTime
set diffTime = currentTime - previousTime
if diffTime >= delayTime (
set previousTime = currentTime
perform user input, game logic, and screen refresh
)
)
And here is actual code that computes the elapsed time since last movement. The currentTime (t2) is measured as centiseconds (1/100 second) since midnight. It is parsed and computed using FOR /F and basic math. The diffTime (tDiff) will be negative if the previousTime (t1) is before midnight and the currentTime (t2) is after midnight. If negative, then 1 day is added to diffTime to get the correct time interval.
%=== compute time since last move ===%
for /f "tokens=1-4 delims=:.," %%a in ("!time: =0!") do set /a "t2=(((1%%a*60)+1%%b)*60+1%%c)*100+1%%d-36610100, tDiff=t2-t1"
if !tDiff! lss 0 set /a tDiff+=24*60*60*100
There is so much more that can be discussed. Try the SNAKE.BAT game, study the post and the code, and see where your imagination can take you.

Answer 2

Some optimizations
1) It's better to use good variable names.
Names like 1, 2 ... 10 are really bad, nobody knows what they are good for, even you self will not remember in a month.
And then it's also a bad idea as it can have many side effects to use variables begining with digits, in batch there are many where these will simply fail.
2) You should combine your output to complete lines before outputting it.
Then you don't need set/p only echo and it's faster.
3) calls to functions like :strlen should be avoided, calls at all are expensive and in your case it should be possible to solve the same without strlen at all.
4) The function :checkshot don't need a for loop.
I don't understand what you try to do there, but you test slen if it is a muliple of 5.
This could be solved with
set /a remainder=slen %% 5
if !remainder! EQU 0 (
...
5) Follow the tips of dbenham :-)