Timer question

[+atari2600land]

I'll try to be as specific as I can with this next question.

How do you activate a timer or time counter thingee?

In this game I'm working on, I want a sprite (player1) to pop up on the screen for a certain amount of time and then disappear. While it's on the screen, I want player0 to touch it. So how do I make the sprite stay on the screen for a certain amount of time using a timer-like thing?

[Luigi301]

Having a variable increase by 1 each time the screen is drawn gives you a counter that ticks once per frame.

[jbanes]

Having a variable increase by 1 each time the screen is drawn gives you a counter that ticks once per frame.

 

While this is a good idea, I'd like to throw in that you'll want to use a 16 bit value for your timer. (After you add 1 to the low byte, add the carry flag to the high byte.) The reason for this is that an 8 bit value has a maximum value of 255. At 60 frames per second, the counter will roll over in a mere 4.25 seconds! With a 16 bit value, the timer can be extended to 1092 seconds (about 18 minutes).

[+atari2600land]

Actually, 4.25 seconds is just about the time I need. I'll try that & see what happens.

[+atari2600land]

What is wrong with this program:

1 rem Ants!
2 set smartbranching on
3 rem l = lives counter
4 rem t = timer counter

220 x=60 : y=60 : score=0 : scorecolor = 62 : l=4
221 a = rand : t=0 
222 if a>150 || a<20 then 221 
223 b = rand
224 if b>80 || b<10 then 223
225 if l=0 then goto 359
230 COLUP0 = 198 : COLUBK = 246 : COLUP1 = 0
240 player0x=x : player0y=y : player1x= a : player1y = b
260 player0:
 %01100110
 %00100100
 %00111100
 %11111111
 %00111100
 %00111100
 %00100100
 %01000010
end
270 player1:
 %10111101
 %01111110
 %00011000
 %10111101
 %01111110
 %00011000
 %10111101
 %01111110
end
280 drawscreen
281 t=t+1
282 if t=255 then l=l-1 : goto 221
290 if joy0up then y=y-1
 if y<10 then y=10
 if y>80 then y=80
300 if joy0down then y=y+1
 if y<10 then y=10
 if y>80 then y=80
310 if joy0left then x=x-1
 if x<20 then x=20
 if x>150 then x=150
320 if joy0right then x=x+1
 if x<20 then x=20
 if x>150 then x=150
330 if collision(player0,player1) score=score+1 : goto 221
340 goto 230

359 rem death
360 COLUBK = 0
380 if switchreset then goto 1
385 goto 360

When I compile this, it gives me a bunch of errors, many of them saying "(1121): Syntax Error ". ']' error, no arg on stack

[MausBoy]

The first thing I notice is you are missing GOTO in your first two IF/THEN statements.

[+atari2600land]

I checked. That wasn't it.

[+atari2600land]

Never mind. I figured it out.