Give the "game" a "title screen" of sorts; click to begin.

README.markdown

@@ -46,10 +46,15 @@ Finish the little demo "game" where you can move a block around the screen with
 the joystick (i.e. bring it up to par with the original demo game that was written
 for SixtyPical)
 
-### Self-reference in signatures
+### `call` routines that are defined further down in the source code
 
-A vector might store [the address of] a routine which changes the vector.  Thus its
+We might have a graph of states that refer to each other and that want to `goto`
-signature might look like `vector foo outputs foo`.  Thus we need to support that.
+each other.  Thus we need this.  We have it for vectors, but we need it for `call`.
+
+### Allow branches to diverge in what they touch
+
+For example, if the routine inputs and outputs `foo`, and one branch of an `if`
+sets `foo` and the other does not touch it, that should be OK.
 
 ### `vector table` type
 

eg/proto-game.60p

@@ -3,7 +3,7 @@
 // ****************************
 
 // ----------------------------------------------------------------
-// Global Variables and System Locations
+// System Locations
 // ----------------------------------------------------------------
 
 byte vic_border @ 53280
@@ -22,17 +22,22 @@ byte table colormap4 @ 56046
 buffer[2048] screen @ 1024
 byte joy2 @ $dc00
 
+// ----------------------------------------------------------------
+// Global Variables
+// ----------------------------------------------------------------
+
 pointer ptr @ 254
 word pos
 word delta
+byte button_down : 0  // effectively static-local to check_button
 
 //
 // Points to the routine that implements the current game state.
 //
 
 vector dispatch_game_state
-  inputs joy2, pos
+  inputs joy2, pos, button_down, dispatch_game_state
-  outputs delta, pos, screen, screen1, dispatch_game_state
+  outputs delta, pos, screen, screen1, button_down, dispatch_game_state
   trashes a, x, y, c, z, n, v, ptr
 
 //
@@ -48,17 +53,16 @@ vector dispatch_game_state
 //
 
 vector cinv
-  inputs joy2, pos
+  inputs joy2, pos, button_down, dispatch_game_state
-  outputs delta, pos, dispatch_game_state, screen, screen1
+  outputs delta, pos, screen, screen1, button_down, dispatch_game_state
   trashes a, x, y, c, z, n, v, ptr
   @ 788
 
 vector save_cinv
-  inputs joy2, pos
+  inputs joy2, pos, button_down, dispatch_game_state
-  outputs delta, pos, dispatch_game_state, screen, screen1
+  outputs delta, pos, screen, screen1, button_down, dispatch_game_state
   trashes a, x, y, c, z, n, v, ptr
 
-
 // ----------------------------------------------------------------
 // Utility Routines
 // ----------------------------------------------------------------
@@ -96,6 +100,37 @@ routine read_stick
     }
 }
 
+// You can repeatedly (i.e. as part of actor logic or an IRQ handler)
+// call this routine.
+// Upon return, if carry is set, the button was pressed then released.
+
+routine check_button
+  inputs joy2, button_down
+  outputs c, button_down
+  trashes a, z, n
+{
+    ld a, button_down
+    if z {
+        ld a, joy2
+        and a, $10
+        if z {
+            ld a, 1
+            st a, button_down
+        }
+        st off, c
+    } else {
+        ld a, joy2
+        and a, $10
+        if not z {
+            ld a, 0
+            st a, button_down
+            st on, c
+        } else {
+            st off, c
+        }
+    }
+}
+
 routine clear_screen
   outputs screen1, screen2, screen3, screen4, colormap1, colormap2, colormap3, colormap4
   trashes a, y, c, n, z
@@ -128,8 +163,8 @@ routine clear_screen
 //
 
 routine game_state_play
-  inputs joy2, pos
+  inputs joy2, pos, button_down, dispatch_game_state
-  outputs delta, pos, dispatch_game_state, screen, screen1
+  outputs delta, pos, screen, screen1, button_down, dispatch_game_state
   trashes a, x, y, c, z, n, v, ptr
 {
     call read_stick
@@ -148,27 +183,28 @@ routine game_state_play
 }
 
 routine game_state_title_screen
-  inputs joy2, pos
+  inputs joy2, pos, button_down, dispatch_game_state
-  outputs delta, pos, screen, screen1, dispatch_game_state
+  outputs delta, pos, screen, screen1, button_down, dispatch_game_state
   trashes a, x, y, c, z, n, v, ptr
 {
-    ld y, 0
+    ld y, 10
     repeat {
-        ld a, 82
+        ld a, 90
         st a, screen1 + y
         inc y
-        cmp y, 18
+        cmp y, 20
-    } until not z
+    } until z
 
     st off, c
-    // jsr check_button
+    call check_button
 
     if c {
         // call clear_screen
-        // jsr init_game
+        // call init_game
         copy game_state_play, dispatch_game_state
     } else {
-        copy game_state_play, dispatch_game_state
+        // This is sort of a hack.  FIXME: let `if` branches diverge this much.
+        copy dispatch_game_state, dispatch_game_state
     }
 
     goto save_cinv
@@ -179,8 +215,8 @@ routine game_state_title_screen
 // *************************
 
 routine our_cinv
-  inputs joy2, pos
+  inputs joy2, pos, button_down, dispatch_game_state
-  outputs delta, pos, dispatch_game_state, screen, screen1
+  outputs delta, pos, screen, screen1, button_down, dispatch_game_state
   trashes a, x, y, c, z, n, v, ptr
 {
     goto dispatch_game_state