diff --git a/codeGenCpu6502/src/prog8/codegen/cpu6502/AsmGen.kt b/codeGenCpu6502/src/prog8/codegen/cpu6502/AsmGen.kt
index fdbbcfd2c..c313b119b 100644
--- a/codeGenCpu6502/src/prog8/codegen/cpu6502/AsmGen.kt
+++ b/codeGenCpu6502/src/prog8/codegen/cpu6502/AsmGen.kt
@@ -813,6 +813,9 @@ class AsmGen6502Internal (
     }
 
     internal fun assignExpressionTo(value: PtExpression, target: AsmAssignTarget) {
+
+        // this is basically the fallback assignment routine, it is RARELY called
+
         when {
             target.datatype.isByteOrBool -> {
                 if (value.asConstInteger()==0) {
diff --git a/docs/source/structpointers.rst b/docs/source/structpointers.rst
index 6137af127..caea0f6dc 100644
--- a/docs/source/structpointers.rst
+++ b/docs/source/structpointers.rst
@@ -132,7 +132,7 @@ dealing with all of them separately.  You first define the struct type like so::
 You can use boolean fields, numeric fields (byte, word, float), and pointer fields (including str, which is translated into ^^ubyte).
 You cannot nest struct types nor put arrays in them as a field.
 Fields in a struct are 'packed' (meaning the values are placed back-to-back in memory), and placed in memory in order of declaration. This guarantees exact size and place of the fields.
-``sizeof()`` knows how to calculate the size of a struct.
+``sizeof()`` knows how to calculate the combined size of a struct, and ``offsetof()`` can be used to get the byte offset of a given field in the struct.
 The size of a struct cannot exceed 1 memory page (256 bytes).
 
 You can copy the whole contents of a struct to another one by assigning the dereferenced pointers::
diff --git a/docs/source/todo.rst b/docs/source/todo.rst
index 51c1d91c5..9d749365f 100644
--- a/docs/source/todo.rst
+++ b/docs/source/todo.rst
@@ -170,6 +170,7 @@ Libraries
 Optimizations
 -------------
 
+- check that expressions such as  targetvar = value1 + value2  , targetvar = value1 ^ value2   etc.   use the target variable directly and not use needless temp var / registers
 - Port benchmarks from https://thred.github.io/c-bench-64/  to prog8 and see how it stacks up.
 - Since fixing the missing zp-var initialization, programs grew in size again because STZ's reappered. Can we add more intelligent (and correct!) optimizations to remove those STZs that might be redundant again?
 - in Identifier: use typedarray of strings instead of listOf? Other places?
diff --git a/examples/c64/sprites.p8 b/examples/c64/sprites.p8
index 98a83f6be..127c805ea 100644
--- a/examples/c64/sprites.p8
+++ b/examples/c64/sprites.p8
@@ -7,17 +7,17 @@ main {
 
     sub start() {
 
-        txt.print("balloon sprites!\n...we are all floating...\n")
+        txt.print("balloon sprites!\n...we are all floating...\nborders are open too\n")
 
         ubyte @zp i
         for i in 0 to 7 {
             c64.set_sprite_ptr(i, &spritedata.balloonsprite)           ; alternatively, set directly:  c64.SPRPTR[i] = $0a00 / 64
-            c64.SPXY[i*2] = 50+25*i
+            c64.SPXY[i*2] = 60+22*i
             c64.SPXY[i*2+1] = math.rnd()
         }
 
-        c64.SPENA = 255                ; enable all sprites
-        sys.set_rasterirq(&irq.irqhandler, 255)     ; enable animation
+        c64.SPENA = 255       ; enable all sprites
+        sys.set_rasterirq(&irq.irqhandler, 248)         ; trigger irq just above bottom border line
     }
 }
 
@@ -25,6 +25,7 @@ main {
 irq {
 
     sub irqhandler() -> bool {
+        c64.SCROLY = 19             ; 24 row mode, preparing for border opening
         c64.EXTCOL--
 
         ; float up & wobble horizontally
@@ -39,6 +40,7 @@ irq {
         }
 
         c64.EXTCOL++
+        c64.SCROLY = 27            ; 25 row mode, border is open
         return true
     }