Extra lives for Alfraroid

Analyzing the code for Alfaroid I have found that the game tests the combination of F1+CODE
Testing in WebMSX I have found that this combination is a cheat that increments the amount of lives up to 99

...
504C : CD 75 41  CALL    $4175 ; 
504F : F5        PUSH    AF    ;  a   = f3 f2 f1 code caps graph cntrl shift
5050 : FE CF     CP    #$CF    ;  $cf=  1  1  0    0    1    1     1     1
...    
4175 : CD 41 01  CALL    $0141 ; BIOS_SNSMAT
4178 : C9        RET           ; 
...

Extra note: the game uses the functions GTSTK and GTTRG for reading both keyboard and joysticks