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I have recently started coding and wanted to try out Pico-8. A game development platform that uses Lua. I watched tutorials on how to create a platformer and have run into an obstacle with my code. Spid in the code is the name of my main sprite and i have organized some of the code into sections: init, update, draw, collisions and player. if anyone can help me with my error please may you keep in mind that i have little to no experience with coding.

Error message:

Runtime error line 26 tab 4
If spid.dy>0 then
attempt to index global 'spid' (a nil value)
at line 26 tab 4

Cart code

pico-8 cartridge // http://www.pico-8.com
version 18
__lua__
--init

function _init()

spid={
 sp=1,
 x=59,
 y=59,
 h=8,
 w=8,
 dx=0,
 dy=0, 
 maxdx=2,
 maxdy=3,
 acc=0.4,
 boost=4,
 anim=0,
 running=false,
 jumping=false,
 falling=false,
 crouching=false,
 flp=false,
 }


 grav=1.2
 friction=0.85



end






-->8
--update

function _update()

 spid.x+=spid.dx
 spid.y+=spid.dy



 spid_update()
 spid_animation()


end
-->8
--draw

function _draw()

cls()
spr(spid.sp,spid.x,spid.y,1,1,spid.flp)
map(0,0)
end
-->8
--collisions

function obj_collision(obj,aim,flag)
 --obj = table and needs x,y,w,h

 local x=obj.x local y=obj.y
 local w=obj.w local h=obj.h

 local x1=0 local y1=0
 local x2=0 local y2=0

 if aim=="left" then
  x1=x-1   y1=y
  x2=x     y2=y+h-1

 elseif aim=="right" then
  x1=x+w   y1=y
  x2=x+w+1 y2=y+h-1

 elseif aim=="up" then
  x1=x+1   y1=y-1
  x2=x+w-1 y2=y

 elseif aim=="down" then
  x1=x     y1=y+h
  x2=x+w   y2=y+h
 end

 -- convert pixels to tiles

 x/=8 y1/=8
 x/=8 y2/=8

 if fget(mget(x1,y1),flag)
 or fget(mget(x1,y2),flag)
 or fget(mget(x2,y1),flag)
 or fget(mget(x2,y2),flag) then
    return true
   else
    return false
  end

end
-->8
--player

function spid_update()

 spid.dy+=grav
 spid.dx*=friction
 end

 if btn(2) then
  spid.dx-=spid.acc
  spid.running=true
  spid.flp=true
  end
 if btn(1) then
  spid.dx+=spid.acc
  spid.running=true
  spid.flp=false
  end

 if btnp(āŽ)
 and spid.landed then
  spid.dy-=spid.boost
  spid.landed=false
 end

 if spid.dy>0 then
  spid.falling=true
  spid.landed=false
  spid.jumping=false
  end
  if obj_collision(spid,"down",0) then
    spid.landed=true
    spid.falling=false
    spid.dy=0
    spid.y-=(spid.y+spid.h)%8

elseif spid.dy<0 then
  spid.jumping=true
  if obj_collision(spid,up,1) then
   spid.dy=0
 end
end



if spid.dx<0 then
 if obj_collision(spid,"left",1) then
  spid.dx=0
 end


elseif spid.dx>0 then
 if obj_collion(spid,"right",1) then    
  spid.dx=0
  end

end
Brettski
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Pterrible
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1 Answers1

3

You have an extra end in your function on tab 4
I am assuming the end on the line after, spid.dx*=friction doesn't belong there. After correcting this pico-8 complains spid_animation() doesn't exist, which it doesn't in the code provided.

function spid_update()

 spid.dy+=grav
 spid.dx*=friction
 end

 if btn(2) then
  spid.dx-=spid.acc
  spid.running=true
  spid.flp=true
  end

May I suggest that you line up your if/end on the same column to keep them straight. This way it is much easier to look down the margin of your code and know which end's go with if statements, functions, etc.

for example, instead of:

 if btn(2) then
  spid.dx-=spid.acc
  spid.running=true
  spid.flp=true
  end

use:

 if btn(2) then
  spid.dx-=spid.acc
  spid.running=true
  spid.flp=true
 end

It seems like a small thing, but when you have a lot of nested code, it will make reading it much easier.

Pico-8 files may also be edited with external editors. I find this specially useful when running into issues like this (non-obvious bugs). For one you can see more of your code at once, and to they can highlight missing/extra end's.

Information on using an external editor is mentioned in the manual included with the executable: https://www.lexaloffle.com/pico-8.php?page=manual

Brettski
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