Add scoring

mato8.asm

@@ -16,6 +16,8 @@ define direction_down 6
 define direction_left 12
 define direction_right 18
 
+define score_high_reg v5
+define score_low_reg v6
 define game_over_reg v7
 define fruit_x_reg v8
 define fruit_y_reg v9
@@ -29,6 +31,9 @@ start:
 	cls
 	ld game_over_reg, 0
 
+	ld score_high_reg, 0
+	ld score_low_reg, 0
+
 	rnd head_x_reg, 63
 	rnd head_y_reg, 31
 
@@ -80,6 +85,8 @@ game_over:
 	ld st, v0
 	call wait
 
+	call display_score
+
 	ld v0, 30
 	call wait
 
@@ -96,6 +103,42 @@ game_over:
 
 	jp start
 
+display_score:
+	cls
+
+	ld i, score_high_bcd
+	ld b, score_high_reg
+	ld i, score_low_bcd
+	ld b, score_low_reg
+
+	ld i, score_low_bcd
+	ld v2, [i]
+	; v0 and v1 are zero, v2 is ones
+	ld v3, v2
+	ld i, score_high_bcd
+	ld v2, [i]
+	; v0 is thousands, v1 is hundreds, v2 is tens
+
+	; Score is a four-digit number stored in v0 to v3
+	ld v4, 0
+	ld v5, 0
+	ld f, v0
+	drw v4, v5, 5
+
+	add v4, 5
+	ld f, v1
+	drw v4, v5, 5
+
+	add v4, 5
+	ld f, v2
+	drw v4, v5, 5
+
+	add v4, 5
+	ld f, v3
+	drw v4, v5, 5
+
+	ret
+
 wait:
 	ld dt, v0
 	wait_loop:
@@ -261,6 +304,8 @@ collision:
 eat_fruit:
 	; Jumping to collision skips tail moving code, so we get the snake
 	; lengthening for free
+	call increment_score
+
 	ld v0, 1
 	ld st, v0
 
@@ -268,8 +313,19 @@ eat_fruit:
 	drw fruit_x_reg, fruit_y_reg, 1
 	jp spawn_fruit
 
+increment_score:
+	; Low register stores 0…9
+	add score_low_reg, 1
+	se score_low_reg, 10
+	ret
+	ld score_low_reg, 0
+	add score_high_reg, 1
+	ret
+
 tail_collision:
 	ld game_over_reg, 1
 	ret
 
 single_pixel: db #80
+score_high_bcd: db 0, 0, 0
+score_low_bcd: db 0, 0, 0