intro/demo: show PETSCII brand name + forbid intro skip

src/intro1.asm

@@ -33,7 +33,7 @@ introreset SUBROUTINE
     bne .colorLoop
 
     ; first raster interrupt line, for moustaches
-    lda #68+19
+    lda #68+18
     sta moustacheLine
 
     rts
@@ -411,6 +411,10 @@ statusMenuReset SUBROUTINE
     MEMSET #$d800, #$02, #280       ; color
     MEMCPY #$400, #SnakeText, #280  ; text
 
+    ; Print PETSCII GLG Programs
+    MEMSET #($6a8 + $d800 - $400), #$02, #200   ; color
+    MEMCPY #$6a8, #GLGProgramsText, #200        ; text
+
     ; Print website
     lda #<intro2string          ; lsb of string address
     sta srcStringPointer        ; put into lsb of source pointer

src/program.asm

@@ -90,6 +90,13 @@ menu SUBROUTINE
 
     ; Intro is finished, now it's time to start the proper game
 .intro0end:
+    ; Are you sure? Maybe the demo-intro is not finished, yet
+    ; We do not want to actually start unless the demo is finished,
+    ; otherwise vertical raster line offset may be != 0
+    lda status
+    cmp #ST_MENU
+    bne .menu
+
     ; Set current level pointer to list start
     lda #<levelsList
     sta levelPointer