keen: add support for partial blocks

games/keen/NOTES

@@ -15,9 +15,15 @@ Memory map:
 
 tiles are 2x4, or 4 bytes each
 	so in theory can have up to 256 of them
-	in 16x16 grid
+	but if we want data to fit in one page then 64 it the maximum
+
+tilemap:
 	tilemap is 256 wide by 40 tall = 10k
 
-Tiles:
-	hard tiles start at 32
+Tile types:
+	 0..26 transparent tiles
+	27..31 items
+	32..39 walkthrough tiles
+	40..63 hard tiles
+
 

games/keen/draw_tilemap.s

@@ -25,7 +25,9 @@ tilemap_outer_loop:
 	sta	GBASH
 
 
-	ldy	#0			; draw row from 0..40
+	ldy	#0			; draw row from 0..39
+					; might be faster to count backwards
+					; but would have to adjust a lot
 
 tilemap_loop:
 	ldx	TILEMAP_OFFSET		; get actual tile number
@@ -58,7 +60,7 @@ not_odd_line:
 
 	cpy	#40			; until done
 	bne	tilemap_loop
-					; FIXME: countdown instead?
+
 
 
 	; row is done, move to next line
@@ -103,18 +105,14 @@ done_move_to_line:
 	;===================================
 	; copy tilemap
 	;===================================
-	; want to copy a 16x10 area from global tileset to local
-
-	; originally 16x10				16x10 = 160 bytes
-	;	extend to 20x12 for full screen?	20x12 = 240 bytes
-
+	; local tilemap subset is 20x12 tiles = 240 bytes
+	;	nicely fits in one page
+	;
 	; big tilemap is 256*40
 	;	so each row is a page
 
 	; TILEMAP_X, TILEMAP_Y specify where in big
 
-	; copy to tilemap
-
 TILEMAP_X_COPY_SIZE = 20
 TILEMAP_Y_COPY_SIZE = 12
 

games/keen/handle_laser.s

@@ -38,7 +38,7 @@ laser_check_tiles:
 
 	ldx	LASER_TILE
 	lda	tilemap,X
-	cmp	#HARD_TILES
+	cmp	#ALLHARD_TILES
 	bcs	destroy_laser
 
 

games/keen/move_keen.s

@@ -2,7 +2,8 @@ KEEN_SPEED	=	$80
 
 YDEFAULT	=	20
 
-HARD_TILES	=	32	; start at 32
+HARDTOP_TILES	=	32	; start at 32
+ALLHARD_TILES	=	40	; start at 40
 
 TILE_COLS	=	20
 
@@ -133,8 +134,8 @@ keen_check_head:
 
 	lda	tilemap,X
 
-	; if tile# < HARD_TILES then we are fine
-	cmp	#HARD_TILES
+	; if tile# < ALLHARD_TILES then we are fine
+	cmp	#ALLHARD_TILES
 	bcc	collide_left_right		; blt
 
 	lda	#0
@@ -162,8 +163,8 @@ check_right_collide:
 	tax
 	lda	tilemap,X
 
-	; if tile# < HARD_TILES then we are fine
-	cmp	#HARD_TILES
+	; if tile# < ALLHARD_TILES then we are fine
+	cmp	#ALLHARD_TILES
 	bcc	done_keen_collide		; blt
 
 	lda	#1				;
@@ -179,8 +180,8 @@ check_left_collide:
 	tax
 	lda	tilemap,X
 
-	; if tile# < HARD_TILES then we are fine
-	cmp	#HARD_TILES
+	; if tile# < ALLHARD_TILES then we are fine
+	cmp	#ALLHARD_TILES
 	bcc	done_keen_collide	; blt
 
 	lda	#1
@@ -328,8 +329,8 @@ check_falling:
 	tax
 	lda	tilemap,X
 
-	; if tile# < HARD_TILES then we fall
-	cmp	#HARD_TILES
+	; if tile# < HARDTOP_TILES then we fall
+	cmp	#HARDTOP_TILES
 	bcs	feet_on_ground		; bge
 
 	;=======================