This example shows a simple starfield by S.Devulder for ugBasic. Modified by M.Spedaletti.

 
 
 CONST numr  =  1000 : REM num of random position in pool 
 CONST nums  =    20 : REM number of stars in starfield
 CONST speed =     8 : REM speed of stars (smaller = faster)
 CONST clock =    50 : REM Number of TI per second
 CONST bg    = BLACK : REM background color
 CONST fg    = WHITE : REM forteground color
 
 DIM xrnd AS POSITION (numr+1)
 DIM yrnd AS POSITION (numr+1)
 
 DIM xtab AS POSITION (nums+1)
 DIM ytab AS POSITION (nums+1)
 
 BITMAP ENABLE (320,200,2)
 CLS bg
 COLOR BORDER bg 
 
 FOR i=0 TO numr
 	xrnd(i) = RND(SCREEN WIDTH)
 	yrnd(i) = RND(SCREEN HEIGHT)
 NEXT
 irnd = 0
 
 FOR i=0 TO nums
 	' REPEAT : c = RND(SCREEN COLORS) : UNTIL c<>bg
 	xtab(i) = RND(SCREEN WIDTH)
 	ytab(i) = RND(SCREEN HEIGHT) 
 	
 	PLOT xtab(i),ytab(i),fg
 NEXT
 
 VAR x0 AS SIGNED WORD = (SCREEN WIDTH / 2)
 VAR y0 AS SIGNED WORD = (SCREEN HEIGHT / 2)
 
 VAR x AS SIGNED WORD = 0
 VAR y AS SIGNED WORD = 0
 VAR z AS SIGNED WORD = 0
 VAR t AS SIGNED WORD = 0
 VAR dx AS SIGNED WORD = 0
 VAR dy AS SIGNED WORD = 0
 
 TI=0: frames = 0
 DO
 	INC frames
 	PLOT x0,y0,WHITE
 	IF TI>=clock THEN 
 		LOCATE 0,0 : PRINT frames;"    ";
 		frames = 0 
 		TI = 0
 	ENDIF
 	FOR i=0 TO nums
 		z = xtab(i)
 		x = z + (z - x0)/speed
 
 		t = ytab(i)	
 		y = t + (t - y0)/speed
 		
 		IF (((x OR y)<0) OR (y>=SCREEN HEIGHT)) OR (x>=SCREEN WIDTH) THEN
 			REPEAT
 				x = xrnd(irnd)
 				y = yrnd(irnd)
 				ADD irnd,1,0 TO numr
 			UNTIL ((x-x0)/speed) AND ((y-y0)/speed)
 		ENDIF
 		
 		xtab(i) = x
 		ytab(i) = y
 		
 		PLOT z,t,bg
 		PLOT x,y,fg
 		'PLOT x,y,bg
 	NEXT
     WAIT VBL
 	joy = JOY(0) : dx = 0 : dy = 0
 	IF joy HAS BIT LEFT  THEN : DEC dx : ENDIF
 	IF joy HAS BIT RIGHT THEN : INC dx : ENDIF
 	IF joy HAS BIT UP    THEN : DEC dy : ENDIF
 	IF joy HAS BIT DOWN  THEN : INC dy : ENDIF
 	IF (dx OR dy)<>0 THEN
 		IF joy HAS BIT FIRE THEN : MUL dx,4 : MUL dy,4 : ENDIF
 		PLOT x0,y0,bg
 		ADD x0,dx,0 TO SCREEN WIDTH
 		ADD y0,dy,0 TO SCREEN HEIGHT
 	ENDIF
 LOOP
 

• contrib_starfield.bas

The instructions here refer to compiling the example from the command line. For Microsoft Windows users we suggest using UGBASIC-IDE, which allows you to compile the example with just one click.

In order to compile and run the example, you need to have the Altirra emulator, and in particular that the altirra executable is accessible.

Then, type this command on the command line:

 # Linux 
 ugbc.atari contrib_starfield.bas -o example.xex
 altirra example.xex
 
 # Windows 
 ugbc.atari.exe contrib_starfield.bas -o example.xex
 altirra example.xex

In order to compile and run the example, you need to have the Altirra emulator, and in particular that the altirra executable is accessible.

Then, type this command on the command line:

 # Linux 
 ugbc.atarixl contrib_starfield.bas -o example.xex
 altirra example.xex
 
 # Windows 
 ugbc.atarixl.exe contrib_starfield.bas -o example.xex
 altirra example.xex

In order to compile and run the example, you need to have the VICE emulator, and in particular that the x64sc executable is accessible.

Then, type this command on the command line:

 # Linux 
 ugbc.c64 contrib_starfield.bas -o example.prg
 x64sc example.prg
 
 # Windows 
 ugbc.c64.exe contrib_starfield.bas -o example.prg
 x64sc example.prg

In order to compile and run the example, you need to have the VICE emulator, and in particular that the x64sc executable is accessible.

Then, type this command on the command line:

 # Linux 
 ugbc.c64reu contrib_starfield.bas -o example.prg
 x64sc -reu example.prg
 
 # Windows 
 ugbc.c64reu.exe contrib_starfield.bas -o example.prg
 x64sc -reu example.prg

In order to run the example, you need to have the YAPE emulator. In particular that the yape executable is accessible.

Then, type this command on the command line:

 # Linux 
 ugbc.plus4 contrib_starfield.bas -o example.prg
 yape example.prg
 
 # Windows 
 ugbc.plus4.exe contrib_starfield.bas -o example.prg
 yape example.prg

In order to run the example, you need to have the VICE emulator. In particular that the xplus4 executable is accessible.

Then, type this command on the command line:

 # Linux 
 ugbc.plus4 contrib_starfield.bas -o example.prg
 xplus4 example.prg
 
 # Windows 
 ugbc.plus4.exe contrib_starfield.bas -o example.prg
 xplus4 example.prg

In order to compile and run the example, you need to have the XROAR emulator, and in particular that the xroar executable is accessible.

Then, type this command on the command line:

 # Linux 
 ugbc.d32 contrib_starfield.bas -o example.bin
 xroar -rompath (your rom path) example.bin
 
 # Windows 
 ugbc.d32.exe contrib_starfield.bas -o example.bin
 xroar.exe -rompath (your rom path) example.bin

In order to compile and run the example, you need to have the XROAR emulator, and in particular that the xroar executable is accessible.

Then, type this command on the command line:

 # Linux 
 ugbc.d64 contrib_starfield.bas -o example.bin
 xroar -rompath (your rom path) example.bin
 
 # Windows 
 ugbc.d64.exe contrib_starfield.bas -o example.bin
 xroar.exe -rompath (your rom path) example.bin

In order to compile and run the example, you need to have the DCMOTO emulator, and in particular that the dcmoto executable is accessible.

Then, type this command on the command line and on the emulator:

 # Linux 
 ugbc.pc128op contrib_starfield.bas -o example.k7
 dcmoto
 (choose BASIC 128)
 CLEAR,&H2FFF: LOADM"CASS:",R: EXEC
 
 # Windows 
 ugbc.pc128op.exe contrib_starfield.bas -o example.k7
 dcmoto
 (choose example.k7)
 (choose BASIC 128)
 CLEAR,&H2FFF: LOADM"CASS:",R: EXEC

In order to compile and run the example, you need to have the DCMOTO emulator, and in particular that the dcmoto executable is accessible.

Then, type this command on the command line and on the emulator:

 # Linux 
 ugbc.pc128op contrib_starfield.bas -o example.k7
 dcmoto
 (choose BASIC 128)
 CLEAR,&H2FFF: LOADM"CASS:",R: EXEC
 
 # Windows 
 ugbc.pc128op.exe contrib_starfield.bas -o example.k7
 dcmoto
 (choose example.k7)
 (choose BASIC 128)
 CLEAR,&H2FFF: LOADM"CASS:",R: EXEC

In order to compile and run the example, you need to have the VICE emulator, and in particular that the xvic executable is accessible.

Then, type this command on the command line:

 # Linux 
 ugbc.vic20 contrib_starfield.bas -o example.prg
 xvic --memory 24k example.prg
 
 # Windows 
 ugbc.vic20.exe contrib_starfield.bas -o example.prg
 xvic --memory 24k example.prg

In order to compile and run the example, you need to have the Speccy emulator, and in particular that the speccy executable is accessible.

Then, type this command on the command line:

 # Linux 
 ugbc.zx contrib_starfield.bas -o example.tap
 Speccy example.tap
 
 # Windows 
 ugbc.zx.exe contrib_starfield.bas -o example.tap
 Speccy example.tap

In order to compile and run the example, you need to have the openMsx or the BlueMSX emulator, and in particular that its executable is accessible.

Then, type this command on the command line:

 # Linux 
 ugbc.msx1 contrib_starfield.bas -o example.rom
 openmsx -cart example.rom
 
 # Windows 
 ugbc.msx1.exe contrib_starfield.bas -o example.rom
 openmsx -cart example.rom

 # Linux 
 ugbc.msx1 contrib_starfield.bas -o example.rom
 bluemsx example.rom
 
 # Windows 
 ugbc.msx1.exe contrib_starfield.bas -o example.rom
 bluemsx example.rom

In order to compile and run the example, you need to have the openMsx or the BlueMSX emulator, and in particular that its executable is accessible.

Then, type this command on the command line:

 # Linux 
 ugbc.coleco contrib_starfield.bas -o example.rom
 openmsx -machine \"COL - ColecoVision\" -cart example.rom
 
 # Windows 
 ugbc.coleco.exe contrib_starfield.bas -o example.rom
 bluemsx -machine \"COL - ColecoVision\" example.rom

 # Linux 
 ugbc.coleco contrib_starfield.bas -o example.rom
 bluemsx /machine \"COL - ColecoVision\" /rom1 example.rom
 
 # Windows 
 ugbc.coleco.exe contrib_starfield.bas -o example.rom
 bluemsx  /machine \"COL - ColecoVision\" /rom1 example.rom

In order to compile and run the example, you need to have the BlueMSX emulator, and in particular that its executable is accessible.

Then, type this command on the command line:

 # Linux 
 ugbc.sc3000 contrib_starfield.bas -o example.rom
 bluemsx /machine \"SEGA - SC-3000\" /rom1 example.rom
 
 # Windows 
 ugbc.sc3000.exe contrib_starfield.bas -o example.rom
 bluemsx  /machine \"SEGA - SC-3000\" /rom1 example.rom

In order to compile and run the example, you need to have the BlueMSX emulator, and in particular that its executable is accessible.

Then, type this command on the command line:

 # Linux 
 ugbc.sg1000 contrib_starfield.bas -o example.rom
 bluemsx /machine \"SEGA - SG-1000\" /rom1 example.rom
 
 # Windows 
 ugbc.sg1000.exe contrib_starfield.bas -o example.rom
 bluemsx  /machine \"SEGA - SG-1000\" /rom1 example.rom

If you have found a problem trying to run this example, if you think there is a bug or, more simply, you would like it to be improved, open an issue for this example on GitHub. Thank you!