Rem open a high res overscan screen with 2 colours, 16 pixels high 
Screen Open 0,704,16,2,Hires
Curs Off : Palette $0,$357 : Cls 0 : Rem turn off cursor,set colours and clear screen 
Rem set position 
Screen Display 0,112,260,,
TXT$="zigzag scroll coded by gaz for all you new starters to the amiga and amos!"
Rem define scrolling area
Def Scroll 1,0,0 To 712,300,-2,0
OFFSET=1 : Rem set offset of character to be printed from txt$  
Rem point AMAL channel 0 to the Screen 
Rem the 'P' command in the amal string is a Pause Command (It only checks the 1st character.)
Rem all those P's are used to pause at the top and the bottom  
Channel 0 To Screen Display 0
AML$="L: For R0=240 To 280 ; Let Y=R0 ; Next R0 ; P ; P ; P ; P ; P ; P ; P ; P ; P ; P ;"
AML$=AML$+"For R0=240 To 280 ; Let Y=520-R0 ; Next R0 ; P ; P ; P ; P ; P ; P ; P ; P ; P ; P ; Jump L"
Rem turn on our amal program 
Amal 0,AML$
Amal On 
Repeat 
   Rem postion cursor offscreen 
   Locate 83,0
   Rem print a character from the txt$
   Rem see the Mid$ command in the manual to see how this works 
   Print Mid$(TXT$,OFFSET,1)
   Rem increase our pointer to point to the next character in txt$
   Rem and check to see if it has run out of letters to point to.If it has
   Rem reset to the start of txt$ 
   Rem all this is done with one command!!
   Add OFFSET,1,1 To Len(TXT$)
   For A=0 To 3
      Scroll 1 : Rem scroll out into view 
      Wait Vbl 
   Next 
Until Mouse Click : Rem exit if mouse click else repeat  
Amal Off : Rem turn off up'n'down amal routine