Playable Prototype
The Phase 1 milestone — one wave of drones, shooting, explosions, lives, score, game over.
Every system from Phase 1 is in place. The ship moves and fires. The bullet travels upward and checks against every drone. Eight drones shift left and right in formation, descending at each edge. Explosions animate in two frames. The HUD shows score, high score, lives and wave number. Death triggers a respawn or game over. This is a playable vertical shooter.
The Program
5 REM === PLAYABLE PROTOTYPE ===
10 BORDER 0: PAPER 0: INK 7: CLS
15 GO SUB 800
20 LET sc = 0: LET hi = 0: LET li = 3
22 LET wv = 1: LET ne = 8: LET sp = 4
24 LET nr = 1
25 DIM e(8): DIM r(8): DIM h(8)
27 DIM b(1): DIM c(1): DIM d(1)
30 FOR i = 1 TO ne
32 LET e(i) = (i - 1) * 2: LET r(i) = 0: LET h(i) = 1
34 NEXT i
36 LET fx = 10: LET fy = 2: LET fd = 1: LET tk = 0
40 LET px = 15: LET py = 20
44 LET d(1) = 0
50 CLS
52 GO SUB 600
55 GO SUB 500
80 REM === game loop ===
85 LET k$ = INKEY$
90 IF k$ = "o" OR k$ = "O" THEN GO SUB 300
95 IF k$ = "p" OR k$ = "P" THEN GO SUB 310
100 IF k$ = " " THEN GO SUB 320
105 GO SUB 350
110 LET tk = tk + 1
115 IF tk >= sp THEN GO SUB 400: LET tk = 0
120 IF fy + nr > 19 THEN GO TO 700
125 GO SUB 600
127 GO SUB 650
140 GO TO 80
300 REM === move left ===
302 IF px <= 1 THEN RETURN
304 PRINT AT py, px; " "
306 LET px = px - 1
308 PRINT AT py, px; INK 7; CHR$ 152
309 RETURN
310 REM === move right ===
312 IF px >= 30 THEN RETURN
314 PRINT AT py, px; " "
316 LET px = px + 1
318 PRINT AT py, px; INK 7; CHR$ 152
319 RETURN
320 REM === fire ===
322 IF d(1) = 1 THEN RETURN
324 LET b(1) = px: LET c(1) = py - 1: LET d(1) = 1
326 PRINT AT c(1), b(1); INK 7; CHR$ 148
328 BEEP 0.01, 20
329 RETURN
350 REM === move bullets ===
352 IF d(1) = 0 THEN RETURN
354 PRINT AT c(1), b(1); " "
356 LET c(1) = c(1) - 1
358 IF c(1) < 1 THEN LET d(1) = 0: RETURN
360 REM check hit
362 LET ht = 0
364 FOR j = 1 TO ne
366 IF h(j) <= 0 THEN GO TO 380
368 LET sx = fx + e(j): LET sy = fy + r(j)
370 IF b(1) = sx AND c(1) = sy THEN LET ht = j: GO TO 382
380 NEXT j
382 IF ht = 0 THEN PRINT AT c(1), b(1); INK 7; CHR$ 148: RETURN
384 LET d(1) = 0: LET h(ht) = 0
386 PRINT AT fy + r(ht), fx + e(ht); INK 2; CHR$ 149
388 BEEP 0.02, -5: BEEP 0.02, -10
390 LET sc = sc + 10: IF sc > hi THEN LET hi = sc
396 RETURN
400 REM === move formation ===
402 FOR i = 1 TO ne
404 IF h(i) <= 0 THEN GO TO 420
406 LET sx = fx + e(i): LET sy = fy + r(i)
408 IF sx >= 1 AND sx <= 30 AND sy >= 1 AND sy <= 21 THEN PRINT AT sy, sx; " "
420 NEXT i
422 LET fx = fx + fd
424 IF fx + 14 > 30 OR fx < 1 THEN LET fd = -fd: LET fy = fy + 1
428 FOR i = 1 TO ne
430 IF h(i) <= 0 THEN GO TO 445
432 LET sx = fx + e(i): LET sy = fy + r(i)
434 IF sx < 1 OR sx > 30 OR sy < 1 OR sy > 21 THEN GO TO 445
442 PRINT AT sy, sx; INK 4; CHR$ 144
445 NEXT i
447 RETURN
500 REM === draw player ===
505 PRINT AT py, px; INK 7; CHR$ 152
508 RETURN
530 REM === player hit ===
534 LET li = li - 1
536 PRINT AT py, px; INK 2; CHR$ 149
538 BEEP 0.1, -10: BEEP 0.1, -15
540 PAUSE 25
542 PRINT AT py, px; " "
544 IF li <= 0 THEN GO TO 700
546 LET px = 15
548 GO SUB 500
549 RETURN
600 REM === draw HUD ===
605 PRINT AT 0, 0; INK 7; BRIGHT 1; "SC:"; sc; " HI:"; hi; " LV:"; li; " W"; wv; " "
610 RETURN
650 REM === check wave clear ===
652 LET w = 0
654 FOR i = 1 TO ne
656 IF h(i) > 0 THEN LET w = 1
658 NEXT i
660 IF w = 1 THEN RETURN
662 PRINT AT 10, 9; INK 7; BRIGHT 1; "WAVE CLEAR!"
664 BEEP 0.1, 12: BEEP 0.1, 16: BEEP 0.2, 19
668 GO SUB 600
670 PAUSE 50
672 PRINT AT 10, 9; " "
674 PRINT AT 12, 7; INK 7; "Well done!"
680 PAUSE 50
685 RETURN
700 REM === game over ===
705 CLS
710 PRINT AT 8, 10; INK 2; BRIGHT 1; "GAME OVER"
715 PRINT AT 10, 7; INK 7; "Score: "; sc
720 PRINT AT 12, 7; INK 7; "High: "; hi
730 PRINT AT 18, 6; INK 7; "Press any key"
735 PAUSE 0
740 LET li = 3: LET sc = 0
745 GO TO 20
800 REM === define UDGs ===
805 FOR i = 0 TO 13
810 FOR j = 0 TO 7
815 READ a
820 POKE USR CHR$ (65 + i) + j, a
825 NEXT j
830 NEXT i
835 RETURN
840 REM UDG A: drone
842 DATA 36, 126, 219, 255, 255, 102, 66, 0
844 REM UDG B: scout
846 DATA 24, 60, 126, 255, 219, 24, 36, 0
848 REM UDG C: tank
850 DATA 126, 255, 255, 255, 255, 255, 126, 0
852 REM UDG D: bomber
854 DATA 66, 231, 255, 126, 60, 90, 36, 0
856 REM UDG E: bullet
858 DATA 16, 56, 16, 16, 0, 0, 0, 0
860 REM UDG F: explosion
862 DATA 36, 153, 66, 129, 66, 153, 36, 0
864 REM UDG G: double shot
866 DATA 84, 170, 84, 170, 84, 170, 84, 0
868 REM UDG H: shield
870 DATA 60, 126, 255, 255, 255, 126, 60, 0
872 REM UDG I: player ship
874 DATA 16, 56, 56, 124, 254, 254, 130, 0
876 REM UDG J: enemy bomb
878 DATA 16, 16, 56, 16, 0, 0, 0, 0
880 REM UDG K: explosion 2
882 DATA 129, 66, 36, 0, 36, 66, 129, 0
884 REM UDG L: shield icon
886 DATA 60, 126, 126, 126, 60, 24, 0, 0
888 REM UDG M: drone frame 2
890 DATA 66, 102, 255, 255, 219, 126, 36, 0
892 REM UDG N: scout frame 2
894 DATA 36, 24, 219, 255, 126, 60, 24, 0
What You Built
Phase 1 delivers a complete single-wave shooter with these systems:
UDG graphics:
- Fourteen custom 8x8 characters defined at startup
- Player ship, bullet, explosion, drone — all UDGs, not text characters
- The game looks like a real Spectrum arcade conversion
Player controls:
- O/P for left/right movement with boundary checks
- SPACE to fire with the one-bullet rule
- Erase-redraw movement pattern throughout
Enemy formation:
- Eight drones in a row tracked with arrays
- Formation movement via shared base offset
- Direction reversal and descent at screen edges
- Invasion fail condition when enemies reach the bottom
Collision and combat:
- Position-based bullet-enemy collision for every drone
- Two-frame explosion animation with sound
- Score tracking with high score persistence
Game flow:
- Three lives with death animation and respawn
- Game over screen with score display
- Loop back to restart
What Works
The core feel of a vertical shooter is present. Aiming the ship, timing shots, watching drones explode, feeling the formation creep closer — all of this works. With one enemy type and one wave, the game is simple. But simple is not incomplete. A single well-tuned wave of drones that moves at the right speed, descends at the right rate, and explodes with satisfying feedback is a real game.
What is Missing
Only one enemy type appears. Only one wave exists — once all drones are destroyed, nothing follows. There are no enemy projectiles, no power-ups, no variety in formation patterns. The game ends too quickly or drags on if the player cannot aim well. Phase 2 adds all of this: three more enemy types, ten waves, bombs, power-ups, and the performance lesson that comes from pushing BASIC to handle it all.
Try This
Play it. Run the game and try to clear all eight drones. How many lives does it take? Is the formation speed fair? Does the descent feel threatening or leisurely?
Tune the feel. Change the tick speed (the variable that controls how often the formation moves). Try values of 2, 4 and 8. Which feels best? The difference between a good game and a frustrating one is often a single variable.