In my pong game, why does my left paddle work but not right?

[s_climax]

My right paddle in my game works rather flawlessly, but for some reason my left does not. Sometimes the left paddle makes the shot. Other times it passes right through it. In my eyes, the left and right paddle's codes are identical. What is wrong with my coding?

Another question that you may find easy to solve is how to I reduce the flickering?

code:

setscreen ("graphics:vga;offscreenonly") var chars : array char of boolean var maxscore, ballcol, timer, ballsize, speed, ballx, bally, lpadx, lpady, rpadx, rpady, dx, dy, lscore, rscore : int timer := 1 ballsize := 5 speed := 2 lscore := 0 rscore := 0 ballx := maxx div 2 bally := maxy div 2 lpadx := 10 lpady := maxy div 2 rpadx := maxx - 10 rpady := maxy div 2 ballcol := 7 colorback (green) cls randint (dx, -2, 2) randint (dy, -2, 2) loop     randint (dx, -2, 2)     randint (dy, -2, 2)     exit when dx ~= 0 and dy ~= 0 end loop put "Enter the number of points you would like to play until." get maxscore cls loop     timer += 1     %Right Paddle Controls     Input.KeyDown (chars)     if chars (KEY_UP_ARROW) and rpady + 20 < maxy then         rpady += 5     end if     if chars (KEY_DOWN_ARROW) and rpady - 20 > 0 then         rpady -= 5     end if     %Left Paddle Controls     if chars ('a') and lpady + 20 < maxy then         lpady += 5     end if     if chars ('z') and lpady - 20 > 0 then         lpady -= 5     end if     if ballx + dx < 10 or ballx + dx > maxx - 10 - ballsize then         dx := -dx     end if     if bally + dy < 10 or bally + dy > maxy - 10 - ballsize then         dy := -dy     end if     ballx += dx * speed     bally += dy * speed     %Right Paddle Collisions     if bally >= rpady - 20 and bally <= rpady + 20 then         if ballx > maxx - 15 - (dx * speed) then             ballcol := 1             if bally > rpady and timer mod 3 = 0 then                 dy += 1             else                 dy -= 1             end if         end if     else         if ballx >= maxx - 15 - (dx * speed) then             ballsize := 5             lscore += 1             ballx := maxx div 2             bally := maxy div 2             loop                 randint (dx, -2, 2)                 randint (dy, -2, 2)                 exit when dx ~= 0 and dy ~= 0             end loop             ballcol := 7             locatexy (maxx div 2, maxy div 2)             put "Red point"             delay (1000)             cls             if dx = 0 then                 dx := 1             end if         end if     end if     %Left Paddle Collisions     if bally >= lpady - 20 and bally <= lpady + 20 then         if ballx < (15 + (dx * speed)) then             ballcol := 4             if bally > lpady and timer mod 3 = 0 then                 dy += 1             else                 dy -= 1             end if         end if     else         if ballx <= 0 + 15 + (dx * speed) then             ballsize := 5             rscore += 1             ballx := maxx div 2             bally := maxy div 2             loop                 randint (dx, -2, 2)                 randint (dy, -2, 2)                 exit when dx ~= 0 and dy ~= 0             end loop             ballcol := 7             locatexy (maxx div 2, maxy div 2)             put "Blue point"             delay (1000)             cls             if dx = 0 then                 dx := 1             end if         end if     end if     %Keep the ball moving relatively horizontal     if dy > 3 then         dy -= 1     elsif dy < -3 then         dy += 1     end if     %Drawing     drawbox (10, 0, maxx - 10, maxy, 7)     drawfilloval (ballx, bally, ballsize, ballsize, ballcol)     drawfillbox (rpadx + 5, rpady - 20, rpadx, rpady + 20, 1)     drawfillbox (lpadx - 5, lpady - 20, lpadx, lpady + 20, 4)     drawline (maxx div 2, 0, maxx div 2, maxy, 7)     View.Update     %Draw the background     /*      drawoval (maxx div 2, maxy div 2, 50, 50, 7)      drawfilloval (maxx div 2, maxy div 2, 5, 5, 7)      drawoval (90, maxy div 4, 40, 40, 7)      drawoval (maxx - 90, maxy div 4, 40, 40, 7)      drawoval (90, maxy - maxy div 4, 40, 40, 7)      drawoval (maxx - 90, maxy - maxy div 4, 40, 40, 7)      drawfilloval (90, maxy div 4, 5, 5, 7)      drawfilloval (maxx - 90, maxy div 4, 5, 5, 7)      drawfilloval (90, maxy - maxy div 4, 5, 5, 7)      drawfilloval (maxx - 90, maxy - maxy div 4, 5, 5, 7)      drawline (maxx div 4 + 15, 0, maxx div 4 + 15, maxy, 7)      drawline (maxx div 4 - 15 + maxx div 2, 0, maxx div 4 - 15 + maxx div 2, maxy, 7)      */     delay (0)     cls     put lscore, "/", maxscore     locatexy (maxx - 20, maxy)     put rscore, "/", maxscore     %Check if the game is over     if lscore >= maxscore then         cls         put "Red Player Wins!"     elsif rscore >= maxscore then         cls         put "Blue Player Wins!"     end if     exit when rscore >= maxscore or lscore >= maxscore end loop

[Paul]

Well, it was flashing so I took off vga and graphics in setscreen, dun think u need them anyway, and it stopped flashing.
I like the color change in the ball.
Well I'm too lazy to go thru all that code so Im just going to give u what I think.
When I look at ur code, it looks like the other team gets a point if the ball hits the line. Your paddle is behind the line. It might be the random slope the ball gets everytime it hits (I really hate the random thing), so the increments bypass the checking. Say the paddle is at 5, the ball was at 8, it moves to 6, then it moves to 4, therefore passing the 5. So I dunno if u already have it, but make it so that it bounces off, if the ball is INSIDE the paddle. Another reason why this might not work is because of the line which ur checking from. The ball stops when it hits the line, since the line and the paddle are so close, the ball might bypass the paddle and hit the line, as I explained above. So try making the part of the code which checks if the ball hit a back wall bugproof by making the line and checking coordinates further away from the paddle.

[s_climax]

Paul Bian wrote:

Well, it was flashing so I took off vga and graphics in setscreen, dun think u need them anyway, and it stopped flashing.

Didn't work for me. Still flashed despite removing the 1st line.

[Paul]

no, I didn't take off "offscreenonly"
so its setscreen ("offscreenonly")

[s_climax]

That worked. Thanks

[s_climax]

Okay. I think I figured out the problems.

code:

if ballx + dx < 10 or ballx + dx > maxx - 10 - ballsize then         dx := -dx     end if     if bally + dy < 10 or bally + dy > maxy - 10 - ballsize then         dy := -dy     end if

should be

code:

if ballx + dx < 10 + ballsize or ballx + dx > maxx - 10 - ballsize then         dx := -dx     end if     if bally + dy < 10 + ballsize or bally + dy > maxy - 10 - ballsize then         dy := -dy     end if

also, this:

code:

%Left Paddle Collisions     if bally >= lpady - 20 and bally <= lpady + 20 then         if ballx < (15 + (dx * speed)) then             ballcol := 4             if bally > lpady and timer mod 3 = 0 then                 dy += 1             else                 dy -= 1             end if         end if     else

should be this:

code:

%Left Paddle Collisions     if bally >= lpady - 20 and bally <= lpady + 20 then         if ballx < (15 + (-dx * speed)) then             ballcol := 4             if bally > lpady and timer mod 3 = 0 then                 dy += 1             else                 dy -= 1             end if         end if     else

It now works fine after those changes. Thanks anyways. I jsut had to think it over a bit and pore through my code and I found those two.

[TheFreshPrince]

from the original old program, the left paddle worked with the a and z keys

[s_climax]

I know that. I wrote the code. My problem was that the collisions were different with the left paddle thatn with the right.