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Store snake's movement to allow longer snake

This commit is contained in:
Juhani Krekelä 2023-01-14 22:02:59 +02:00
parent c632573f90
commit 76ceb71e93
1 changed files with 83 additions and 8 deletions
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91
mato8.asm
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@ -16,9 +16,11 @@ define direction_down 6
define direction_left 12
define direction_right 18
define game_over_reg v9
define fruit_x_reg va
define fruit_y_reg vb
define game_over_reg v7
define fruit_x_reg v8
define fruit_y_reg v9
define tail_x_reg va
define tail_y_reg vb
define head_direction_reg vc
define head_x_reg vd
define head_y_reg ve
@ -30,6 +32,9 @@ start:
rnd head_x_reg, 63
rnd head_y_reg, 31
ld tail_x_reg, head_x_reg
ld tail_y_reg, head_y_reg
ld head_direction_reg, direction_right
ld i, single_pixel
@ -131,25 +136,95 @@ turn_right:
ret
move_snake:
; Save the direction the snake is moving at head's location
ld v0, head_x_reg
ld v1, head_y_reg
call direction_table_index
ld v0, head_direction_reg
call unpack_direction
ld [i], v0
ld v2, head_x_reg
; Move the snake's head
call unpack_direction
add head_x_reg, v0
ld v0, 63
and head_x_reg, v0
ld v3, head_y_reg
add head_y_reg, v1
ld v0, 31
and head_y_reg, v0
; Draw head location and erase tail location
ld i, single_pixel
drw head_x_reg, head_y_reg, 1
se vf, 0
call collision
drw v2, v3, 1
drw tail_x_reg, tail_y_reg, 1
; Load the direction the snake was moving at tail's location
ld v0, tail_x_reg
ld v1, tail_y_reg
call direction_table_index
ld v0, [i]
; Move the snake's tail
call unpack_direction
add tail_x_reg, v0
ld v0, 63
and tail_x_reg, v0
add tail_y_reg, v1
ld v0, 31
and tail_y_reg, v0
ret
direction_table_index:
; v0 is the X coördinate, from 0 to 63, 00xxxxxx
; v1 is the Y coördinate, from 0 to 31, 000yyyyy
shl v0, v0
shl v0, v0
; v0 is the X coördinate shifted left by two, xxxxxx00
ld v2, %11100000
and v2, v0
or v1, v2
; v1 is combination of high 3 bits of X coördinate and the Y coördinate, xxxyyyyy
ld v2, %00011100
and v0, v2
; v0 is the low 3 bits of the X coördinate shifted left by two, 000xxx00
jp v0, direction_table_index_table
direction_table_index_table:
; 0
ld i, #400
jp direction_table_index_end
; 1
ld i, #500
jp direction_table_index_end
; 2
ld i, #600
jp direction_table_index_end
; 3
ld i, #700
jp direction_table_index_end
; 4
ld i, #800
jp direction_table_index_end
; 5
ld i, #900
jp direction_table_index_end
; 6
ld i, #a00
jp direction_table_index_end
; 7
ld i, #b00
direction_table_index_end:
add i, v1
ret
unpack_direction: