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Elite on the BBC Micro

Missions: BRIEF [Disc version, Docked]

Name: BRIEF [Show more] Type: Subroutine Category: Missions Summary: Start mission 1 and show the mission briefing
Context: See this subroutine in context in the source code Variations: See code variations for this subroutine in the different versions References: This subroutine is called as follows: * DOENTRY calls BRIEF

This routine does the following: * Clear the screen * Display "INCOMING MESSAGE" in the middle of the screen * Wait for 2 seconds * Clear the screen * Show the Constrictor rolling and pitching in the middle of the screen * Do this for 64 loop iterations * Move the ship away from us and up until it's near the top of the screen * Show the mission 1 briefing in extended token 10 The mission briefing ends with a "{display ship, wait for key press}" token, which calls the PAUSE routine. This continues to display the rotating ship, waiting until a key is pressed, and then removes the ship from the screen.
.BRIEF LSR TP \ Set bit 0 of TP to indicate that mission 1 is now in SEC \ progress ROL TP JSR BRIS \ Call BRIS to clear the screen, display "INCOMING \ MESSAGE" and wait for 2 seconds JSR ZINF \ Call ZINF to reset the INWK ship workspace LDA #CON \ Set the ship type in TYPE to the Constrictor STA TYPE JSR NWSHP \ Add a new Constrictor to the local bubble (in this \ case, the briefing screen) LDA #1 \ Move the text cursor to column 1 STA XC STA INWK+7 \ Set z_hi = 1, the distance at which we show the \ rotating ship JSR TT66 \ Clear the top part of the screen, draw a white border, \ and set the current view type in QQ11 to 1 LDA #64 \ Set the main loop counter to 64, so the ship rotates STA MCNT \ for 64 iterations through MVEIT .BRL1 LDX #%01111111 \ Set the ship's roll counter to a positive roll that STX INWK+29 \ doesn't dampen STX INWK+30 \ Set the ship's pitch counter to a positive pitch that \ doesn't dampen JSR LL9 \ Draw the ship on screen JSR MVEIT \ Call MVEIT to rotate the ship in space DEC MCNT \ Decrease the counter in MCNT BNE BRL1 \ Loop back to keep moving the ship until we have done \ all 64 iterations .BRL2 LSR INWK \ Halve x_lo so the Constrictor moves towards the centre INC INWK+6 \ Increment z_lo so the Constrictor moves away from us BEQ BR2 \ If z_lo = 0 (i.e. it just went past 255), jump to BR2 \ to show the briefing INC INWK+6 \ Increment z_lo so the Constrictor moves a bit further \ away from us BEQ BR2 \ If z_lo = 0 (i.e. it just went past 255), jump out of \ the loop to BR2 to stop moving the ship up the screen \ and show the briefing LDX INWK+3 \ Set X = y_lo + 1 INX CPX #112 \ If X < 112 then skip the next instruction BCC P%+4 LDX #112 \ X is bigger than 112, so set X = 112 so that X has a \ maximum value of 112 STX INWK+3 \ Set y_lo = X \ = y_lo + 1 \ \ so the ship moves up the screen (as space coordinates \ have the y-axis going up) JSR LL9 \ Draw the ship on screen JSR MVEIT \ Call MVEIT to move and rotate the ship in space JMP BRL2 \ Loop back to keep moving the ship up the screen and \ away from us .BR2 INC INWK+7 \ Increment z_hi, to keep the ship at the same distance \ as we just incremented z_lo past 255 LDA #10 \ Set A = 10 so the call to BRP prints extended token 10 \ (the briefing for mission 1 where we find out all \ about the stolen Constrictor) BNE BRPS \ Jump to BRP via BRPS to print the extended token in A \ and show the Status Mode screen), returning from the \ subroutine using a tail call (this BNE is effectively \ a JMP as A is never zero)