Add "Press space to start"

src/main.asm

@@ -155,10 +155,33 @@ loading_feedback SUBROUTINE
     ldx loading_bar
     lda #$79
     sta 7988,x
+
+    cpx #21
+    beq .start_button
+    rts
+.start_button:
+    ; print
+    lda #<start_button_message
+    ldy #>start_button_message
+    jsr $cb1e
+
+    ; use system CHRIN
+    lda #$e0
+    sta $324
+    lda #$f2
+    sta $325
+
+.chrin:
+    jsr $ffe4
+    cmp #$20
+    bne .chrin
+
     rts
 
 message:
     BYTE #$0d,#$0d,"PLEASE WAIT 20 SEC",#$0d,"I'M JUST",#$0d,"AN OLD COMPUTER",#$0d,#0
+start_button_message:
+    BYTE "PRESS SPACE TO START",#$0
 
 ; https://www.commodore.ca/manuals/funet/cbm/vic20/demos.basic/unexpanded/Stillenacht.prg
 demo_start: