fix stack-variable accesses

ray.asm

@@ -39,7 +39,7 @@ com_file: equ 0
 
  int 0x10 ; Call BIOS.
 
- enter total-2,0 ; Make space for internal variables,
+ enter total,0 ; Make space for internal variables,
  ; and use BP to refer them.
 
  push 0xa000 ; Point to video RAM.
@@ -296,24 +296,24 @@ const_1_4: dd 1.4
  ;
  ; Variables are kept on the stack to make instructions shorter.
  ;
-var_n: equ base+$02 ; Integer
-var_m: equ base+$04 ; Integer
-pixel: equ base+$06 ; Integer
-var_u: equ base+$08 ; u - Ray direction (normalized)
-var_v: equ base+$0c ; v - Ray direction (normalized)
-var_w: equ base+$10 ; w - Ray direction (normalized)
-var_x: equ base+$14 ; x - Origin of ray
-var_y: equ base+$18 ; y - Origin of ray
-var_z: equ base+$1c ; z - Origin of ray
-var_e: equ base+$20 ; e - Position of sphere
-var_f: equ base+$24 ; f - Position of sphere
-var_g: equ base+$28 ; g - Position of sphere
-var_p: equ base+$2c ; Float
-var_d: equ base+$30 ; Float
-var_t: equ base+$34 ; Float
-var_i: equ base+$38 ; Float
-var_a: equ base+$3c ; Float
-var_s: equ base+$40 ; Float
+var_n: equ -$42 ; Integer
+var_m: equ -$40 ; Integer
+pixel: equ -$3e ; Integer
+var_u: equ -$3c ; u - Ray direction (normalized)
+var_v: equ -$38 ; v - Ray direction (normalized)
+var_w: equ -$34 ; w - Ray direction (normalized)
+var_x: equ -$30 ; x - Origin of ray
+var_y: equ -$1c ; y - Origin of ray
+var_z: equ -$28 ; z - Origin of ray
+var_e: equ -$24 ; e - Position of sphere
+var_f: equ -$20 ; f - Position of sphere
+var_g: equ -$1c ; g - Position of sphere
+var_p: equ -$18 ; Float
+var_d: equ -$14 ; Float
+var_t: equ -$10 ; Float
+var_i: equ -$0c ; Float
+var_a: equ -$08 ; Float
+var_s: equ -$04 ; Float
 
 total: equ base+$44