Drawing BG graphics with $61, $62.

20 E9 EC = the drawstring routine.

It will provide a $61 and $62 definition as 
well as the tile numbers for each tile drawn. 
"FE" means continue the draw at another row 
and column; "FF" means conclude the draw.

$61 = The row the graphic chunk is placed
$62 = The col the graphic chunk is placed



At 0x3D260, tiles are used to form a TSA block. 
In here it is probable that there is a check 
for collision. Ay 0x398F4 begins a decrement of 
$520 when the player is falling. Collision 
ceases at 0x397E5. Wow. $6E0(with x)... That 
set of ram... are blocks in the room with collision!!

0x3D3B9 is a check for 770 (with Y).

Each bg tileset contains 64 tiles. 

Each byte in the $6E0 array represents a pair 4 tile 
square blocks situated side by side, like this:

 _ _ _ _ _ _ _ _
|       |       |

|       |       | 
 _ _ _ _ _ _ _ _

The first nybble is the left block, the second the right.

00 00 00 00 00 00 00 66
00 00 00 00 00 00 00 66
00 00 00 00 00 00 00 66
00 00 00 00 00 00 00 66
00 00 00 00 00 00 00 66
00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00
00 00 00 00 00 00 66 66
00 00 00 00 66 66 66 66
66 66 66 66 66 66 66 66

The top of all the blocks are solid. Somehow, 6 represents 
this.


