# Collision function for multi sprites

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I used this example to distinguish which item is being hit by the player, I tried to be economical

``` set kernel multisprite

player0x =  10: player0y = 88
player1x =  80: player1y = 78
player2x =  30: player2y = 65
player3x =  90: player3y = 52
player4x = 110: player4y = 39
player5x = 130: player5y = 26

player0:
%01111110
%10000011
%10110011
%10101011
%10101011
%10101011
%10011011
%10000011
%10101011
%11010110
%01111100
end

player1:
%01101111
%10000011
%10111011
%10010011
%10010011
%10110011
%10010011
%10000011
%10101011
%11000110
%01101100
end

player2:
%01101111
%10000011
%10111011
%10100011
%10111011
%10001011
%10111011
%10000011
%10101011
%11000110
%01101100
end

player3:
%01101111
%10000011
%10110011
%10001011
%10011011
%10001011
%10110011
%10000011
%10101011
%11000110
%01101100
end

player4:
%01101111
%10000011
%10001011
%10001011
%10111011
%10101011
%10101011
%10000011
%10101011
%11000110
%01101100
end

player5:
%01101111
%10000011
%10111011
%10001011
%10111011
%10100011
%10111011
%10000011
%10101011
%11000110
%01101100
end

COLUBK = 56
_COLUP1 = 18: rem coloring player1 _
COLUP2 = 25
COLUP3 = 10
COLUP4 = 45
COLUP5 = 60

loop
COLUP0 = 155: rem color player0 must be updated

control
if joy0up    && player0y <  82 then player0y = player0y + 1
if joy0down  && player0y >  29 then player0y = player0y - 1
if joy0left  && player0x >  16 then player0x = player0x - 1
if joy0right && player0x < 136 then player0x = player0x + 1

colidir
y = colide(player0x, player1x, player0y, player1y)
if y then player1x = (rand&127)+20

y = colide(player0x, player2x, player0y, player2y)
if y then player2x = (rand&127)+20

y = colide(player0x, player3x, player0y, player3y)
if y then player3x = (rand&127)+20

y = colide(player0x, player4x, player0y, player4y)
if y then player4x = (rand&127)+20

y = colide(player0x, player5x, player0y, player5y)
if y then player5x = (rand&127)+20

drawscreen
goto loop

function colide
y = temp1 + 9: x = temp2 - 7
if y > x && temp1 < temp2 then y = temp3 -13: x = temp4 -10: if temp3 > x && y < temp4 then return 1
return 0

rem p0 width  9,  p0 height -13
rem px width -7,  px height -10

```

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On 2/19/2021 at 6:47 AM, Gemintronic said:

They always pass two parameters whether you specify them or not (but bB is likely to complain if you don't pass any parameters)

You can sometimes sort of use them in place of an operand or an expression

But I'd just use a subroutine.  More predicable.

Functions are so finicky they're almost (but not quite) useless

Subroutines have overhead, but not much.

A gosub uses 12 cycles and two bytes of the stack

a = b + c uses 11 cycles

Depending on the kernel, the stack might be only 6 bytes so you could only go 3 levels deep provided

you don't use any expressions that use stack (and I think drawscreen goes 3 deep)

And the way bB uses the stack in expressions is all kinds of goofy

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