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BBC Micro Elite

Stardust: nWq

Name: nWq [View in context] Type: Subroutine Category: Stardust Summary: Create a random cloud of stardust
Create a random cloud of stardust containing the correct number of dust particles, i.e. NOSTM of them, which is 3 in witchspace and 18 (#NOST) in normal space. Also clears the scanner and initialises the LSO block. This is called by the DEATH routine when it displays our untimely demise.
.nWq LDY NOSTM \ Set Y to the current number of stardust particles, so \ we can use it as a counter through all the stardust .SAL4 JSR DORND \ Set A and X to random numbers ORA #8 \ Set A so that it's at least 8 STA SZ,Y \ Store A in the Y-th particle's z_hi coordinate at \ SZ+Y, so the particle appears in front of us STA ZZ \ Set ZZ to the particle's z_hi coordinate JSR DORND \ Set A and X to random numbers STA SX,Y \ Store A in the Y-th particle's x_hi coordinate at \ SX+Y, so the particle appears in front of us STA X1 \ Set X1 to the particle's x_hi coordinate JSR DORND \ Set A and X to random numbers STA SY,Y \ Store A in the Y-th particle's y_hi coordinate at \ SY+Y, so the particle appears in front of us STA Y1 \ Set Y1 to the particle's y_hi coordinate JSR PIXEL2 \ Draw a stardust particle at (X1,Y1) with distance ZZ DEY \ Decrement the counter to point to the next particle of \ stardust BNE SAL4 \ Loop back to SAL4 until we have randomised all the \ stardust particles \ Fall through into WPSHPS to clear the scanner and \ reset the LSO block