Weird issue in a function

[swapd0]

I've been playing a bit with 7800basic and I'm stuck with a weird error.

 

I've a function to check collisions with a 8x8 tile map, but since I'm using 16pixels zones the collision it's a bit weird because the tiles are 8x16 but they represents 4x8 tiles. hit_tile_xxx are arrays of data with a bitmask to check if you have to collided with the tile.

 

I've a big wall on the left side of the screen, if I move the sprite there and then move it vertically I get the background color changing, and it's weird because I'm testing with temp1 that holds x position and I'm not moving on x axis.

 

temp & 8 and temp & 4 are used to test if I'm in the left/upper or right/lower part of the tile.

 

It looks like temp1 it's smashed with temp2 somewhere...

 

Quote

; parameters, x, y

function tile_collision

  tx = temp1 / 8

  ty = temp2 / 16

  tile = peekchar(screen1map, tx, ty, 20, 12)

  if tile = 0 then return 0

  tile = tile / 2. ; because of doublewide

  char1 = tile. ; debug 

  if temp2 & 8 then hit = hit_tile_high[tile] else hit = hit_tile_low[tile]. ; A

  if hit && (temp1 & 4) then BACKGRND = $5f : hit = hit_tile_right[tile] else BACKGRND = $1f : hit = hit_tile_left[tile]. ; B

  return hit

 

Edited February 15, 2021 by swapd0

[CloakeD]

https://www.randomterrain.com/7800basic.html#temporary_variables

 

I was overwriting the temp variables,this helped me.

Edited February 15, 2021 by CloakeD