Bunza Building Lights

#define numleds  15
byte ledpins [ ] =  { 0,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17 } ;
void setup( )  {
    for ( int  i=1; i <= numleds;  i++ )  {
    pinMode ( ledpins [ i ], OUTPUT) ;
    digitalWrite ( ledpins [ i ] , HIGH) ;
   }
   pinMode (2,INPUT);      // Pin 2 will be the control pin for this lighting group
   digitalWrite (2,HIGH);    //This turns the Pull up ON
}
void loop ( )  {
                digitalWrite ( ledpins [ random ( 0, numleds+1 ) ], lightsw ( ) ) ;
                delay ( 900 ) ;
}
boolean lightsw ( )  {
 if (digitalRead(2)  == LOW) return LOW;  //If the group control pin is LOW ALL lights
                                                             // will eventually turn OFF
 if  ( random (0,100) > 40 ) return LOW ;
   else return HIGH ;
}