diff --git a/README.md b/README.md
index a396a6d..d16a403 100644
--- a/README.md
+++ b/README.md
@@ -3,8 +3,10 @@ SixtyPical
 
 _Version 0.21.  Work-in-progress, everything is subject to change._
 
+**SixtyPical** brings [extended static checking][] to the [6502][].
+
 **SixtyPical** is a [low-level](#low-level) programming language
-supporting a sophisticated [static analysis](#static-analysis).
+supporting some advanced [static analysis](#static-analysis) methods.
 Its reference compiler can generate [efficient code](#efficient-code) for
 several 6502-based [target platforms](#target-platforms) while catching many
 common mistakes at compile-time, reducing the time spent in debugging.
@@ -124,7 +126,9 @@ Documentation
 *   [Output formats supported by `sixtypical`](doc/Output%20Formats.md)
 *   [TODO](TODO.md)
 
+[6502]: https://en.wikipedia.org/wiki/MOS_Technology_6502
 [MOS Technology 6502]: https://en.wikipedia.org/wiki/MOS_Technology_6502
+[extended static checking]: https://en.wikipedia.org/wiki/Extended_static_checking
 [effect system]: https://en.wikipedia.org/wiki/Effect_system
 [abstractly interprets]: https://en.wikipedia.org/wiki/Abstract_interpretation
 [calling conventions]: https://en.wikipedia.org/wiki/Calling_convention
diff --git a/TODO.md b/TODO.md
index 7b08e56..8be7282 100644
--- a/TODO.md
+++ b/TODO.md
@@ -55,6 +55,14 @@ What happens if a routine calls itself, directly or indirectly?  Many
 constraints might be violated in this case.  We should probably disallow
 recursion by default.  (Which means assembling the callgraph in all cases.)
 
+However note, it's okay for a routine to goto itself.  It's a common
+pattern for implementing a state machine, for a routine to tail-goto a
+vector, which might contain the address of the same routine.
+
+The problems only come up, I think, when a routine calls itself re-entrantly.
+
+So the callgraph would need to distinguish between these two cases.
+
 ### Analyze memory usage
 
 If you define two variables that occupy the same address, an analysis error ought
@@ -83,6 +91,23 @@ Implementation
 For analysis errors, there is a line number, but it's the line of the routine
 after the routine in which the analysis error occurred.  Fix this.
 
+### Better selection of options
+
+`-O` should turn on the standard optimizations.
+
+There should maybe be a flag to turn off tail-call optimization.
+
+Some options should automatically add the appropriate architecture include
+directory to the path.
+
+Distribution
+------------
+
+### Demo game
+
+Seems you're not be able to get killed unless you go off the top or bottom of
+the screen?  In particular, you cannot collide with a bar?
+
 Blue-skying
 -----------
 
diff --git a/eg/README.md b/eg/README.md
index 9268429..289839c 100644
--- a/eg/README.md
+++ b/eg/README.md
@@ -13,24 +13,8 @@ to serve as manual integration test cases.  See
 In the [c64](c64/) directory are programs that run on the Commodore 64.
 The directory itself contains some simple demos, for example
 [hearts.60p](c64/hearts.60p), while there are subdirectories for more
-elaborate demos:
-
-*   [demo-game](c64/demo-game/): a little game-like program written as a
-    "can we write something you'd see in practice?" test case for SixtyPical.
-    
-*   [ribos](c64/ribos/): a well-commented example of a C64 raster interrupt
-    routine. Originally written with the P65 assembler (which has since
-    been reborn as [Ophis][]).
-    
-    The second version of Ribos has been translated to SixtyPical.
-    
-*   [petulant](c64/petulant/): "The PETulant Cursor", a tiny (44 bytes)
-    "display hack". Originally written in the late 80's. Rewritten with
-    the P65 assembler (now Ophis) and re-released on April 1st, 2008 (a
-    hint as to its nature).
-    
-    Translated to SixtyPical (in 2018), after adding some optimizations
-    to the SixtyPical compiler, the resulting executable is still 44 bytes!
+elaborate demos, like the flagship demo game.  See
+[the README in that directory](c64/README.md) for details.
 
 ### vic20
 
diff --git a/eg/c64/README.md b/eg/c64/README.md
index a953e06..b63c514 100644
--- a/eg/c64/README.md
+++ b/eg/c64/README.md
@@ -1,5 +1,23 @@
 This directory contains SixtyPical example programs
 specifically for the Commodore 64.
 
-See the [README in the parent directory](../README.md) for
-more information on these example programs.
+There are subdirectories for more elaborate demos:
+
+*   [demo-game](demo-game/): a little game-like program written as a
+    "can we write something you'd see in practice?" test case for SixtyPical.
+    
+*   [ribos](ribos/): a well-commented example of a C64 raster interrupt
+    routine. Originally written with the P65 assembler (which has since
+    been reborn as [Ophis][]).
+    
+    The second version of Ribos has been translated to SixtyPical.
+    
+*   [petulant](petulant/): "The PETulant Cursor", a tiny (44 bytes)
+    "display hack". Originally written in the late 80's. Rewritten with
+    the P65 assembler (now Ophis) and re-released on April 1st, 2008 (a
+    hint as to its nature).
+    
+    Translated to SixtyPical (in 2018), after adding some optimizations
+    to the SixtyPical compiler, the resulting executable is still 44 bytes!
+
+[Ophis]: http://michaelcmartin.github.io/Ophis/
diff --git a/eg/c64/demo-game/demo-game.60p b/eg/c64/demo-game/demo-game.60p
index 027f2cc..11fcc8d 100644
--- a/eg/c64/demo-game/demo-game.60p
+++ b/eg/c64/demo-game/demo-game.60p
@@ -2,7 +2,7 @@
 // * Demo Game for SixtyPical *
 // ****************************
 
-include "joy2delta.60p"
+include "joystick.60p"
 
 // ----------------------------------------------------------------
 // Type Definitions
@@ -103,38 +103,6 @@ vector game_state_routine
 // Utility Routines
 // ----------------------------------------------------------------
 
-// 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.
-
-define check_button routine
-  inputs joy2
-  outputs c
-  trashes a, z, n
-  static byte button_down : 0
-{
-    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
-        }
-    }
-}
-
 define clear_screen routine
   outputs screen, colormap
   trashes a, y, c, n, z
diff --git a/eg/c64/demo-game/run.sh b/eg/c64/demo-game/run.sh
new file mode 100755
index 0000000..1086985
--- /dev/null
+++ b/eg/c64/demo-game/run.sh
@@ -0,0 +1,23 @@
+#!/bin/sh
+
+# This script builds and runs the demo game.  You need
+# the VICE emulatore installed, in particular VICE's x64.
+
+# You might want a `vicerc` file like the following:
+# [C64]
+# VICIIDoubleScan=0
+# VICIIDoubleSize=0
+# KeySet1NorthWest=0
+# KeySet1North=273
+# KeySet1NorthEast=0
+# KeySet1East=275
+# KeySet1SouthEast=0
+# KeySet1South=274
+# KeySet1SouthWest=0
+# KeySet1West=276
+# KeySet1Fire=306
+# KeySetEnable=1
+# JoyDevice1=0
+# JoyDevice2=2
+
+../../../bin/sixtypical --run-on x64 -I ../../../include/c64/ demo-game.60p
diff --git a/eg/c64/joystick.60p b/eg/c64/joystick-demo.60p
similarity index 89%
rename from eg/c64/joystick.60p
rename to eg/c64/joystick-demo.60p
index 0558426..faeb949 100644
--- a/eg/c64/joystick.60p
+++ b/eg/c64/joystick-demo.60p
@@ -1,4 +1,4 @@
-include "joy2delta.60p"
+include "joystick.60p"
 
 word screen @ 1024
 
diff --git a/include/c64/joy2delta.60p b/include/c64/joy2delta.60p
deleted file mode 100644
index ff1b583..0000000
--- a/include/c64/joy2delta.60p
+++ /dev/null
@@ -1,36 +0,0 @@
-byte joy2 @ $dc00
-
-word delta
-
-define read_stick routine
-  inputs joy2
-  outputs delta
-  trashes a, x, z, n
-{
-    ld x, joy2
-    ld a, x
-    and a, 1                   // up
-    if z {
-        copy $ffd8, delta      // -40
-    } else {
-        ld a, x
-        and a, 2               // down
-        if z {
-            copy word 40, delta
-        } else {
-            ld a, x
-            and a, 4               // left
-            if z {
-                copy $ffff, delta  // -1
-            } else {
-                ld a, x
-                and a, 8           // right
-                if z {
-                    copy word 1, delta
-                } else {
-                    copy word 0, delta
-                }
-            }
-        }
-    }
-}
diff --git a/include/c64/joystick.60p b/include/c64/joystick.60p
new file mode 100644
index 0000000..faf41c1
--- /dev/null
+++ b/include/c64/joystick.60p
@@ -0,0 +1,71 @@
+byte joy2 @ $dc00
+
+word delta
+
+// Read the joystick and compute the delta it represents
+// in a row-based 40-column grid like the C64's screen.
+
+define read_stick routine
+  inputs joy2
+  outputs delta
+  trashes a, x, z, n
+{
+    ld x, joy2
+    ld a, x
+    and a, 1                   // up
+    if z {
+        copy $ffd8, delta      // -40
+    } else {
+        ld a, x
+        and a, 2               // down
+        if z {
+            copy word 40, delta
+        } else {
+            ld a, x
+            and a, 4               // left
+            if z {
+                copy $ffff, delta  // -1
+            } else {
+                ld a, x
+                and a, 8           // right
+                if z {
+                    copy word 1, delta
+                } else {
+                    copy word 0, delta
+                }
+            }
+        }
+    }
+}
+
+// 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.
+
+define check_button routine
+  inputs joy2
+  outputs c
+  trashes a, z, n
+  static byte button_down : 0
+{
+    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
+        }
+    }
+}