Bēmaga, 30 years later — porting a 100-line BASIC game to iPhone

Heads up — this one has nothing to do with parenting. There was this 80s Japanese hobby-programming magazine called Microcomputer BASIC Magazine, but everyone just called it Bēmaga. Every issue printed the full source code of a small game; you'd type the whole thing into your PC-9801 by hand. I took one — a 2-player tennis game called Receive No.1 — and ported the entire 100-line N88-BASIC listing to iPhone, line for line. Plus the one thing the original couldn't pull off in 1990s hardware: a CPU opponent, trained with a Genetic Algorithm.

Nothing to do with parenting today. If anything, my kid probably wouldn't get the appeal of this one.

I brought Receive No.1 back, 30 years later, on iPhone.

Quick context for folks outside Japan: in the 80s and 90s there was a magazine called マイコン BASIC マガジン (everyone shortened it to ベーマガ / Bēmaga). It was a hobbyist-programming monthly, and the wild thing about it was that every issue printed the full source listing of a tiny game right there in the magazine. You'd buy the issue, sit at your PC-9801, and type the entire thing in by hand, line number by line number. Receive No.1 was one of those — a 2-player tennis game written in N88-BASIC (a Microsoft-licensed BASIC dialect that shipped on NEC PCs), in about 100 lines.

Same code. Same physics. Same bugs, probably.

670 BEEP:IF SU=T THEN SU=ABS(SU-3) ELSE P(SU)=P(SU)+1
680 GOSUB *TOKUTENKAKU:IF P(SU)=15 THEN GOTO *SHOUHAI

From that scoring line, all the way down to BX=BX+VX:BY=BY+VY/1.5:VY=VY+1 for the gravity model, HX=X+7+32*CS(AA), HY=Y+31*SN(AA) for the arm hit-box, and a DIM CS(360), SN(360) lookup table holding sin/cos at 22.5° steps — I moved the original logic onto a phone, verbatim.

Because the physics matches, all of the original quirks carry over:

• Serve goes straight up from the corner and falls back down
• The exact frame you snap your arm decides the ball's angle and speed
• Three touches and the ball is dead
• Only the server can score (old-school tennis rules)

The thing 1990s hardware couldn't do: a CPU opponent

• CPU that gets better. 20 genes that evolve through play. I let one run locally for about 1500 generations and shipped that as the "starter CPU." Genetic Algorithm wasn't on the table in the original Bēmaga listing. You can keep training your own, export it as JSON, and hand it to a friend.
• Watch mode. Two CPUs play each other and you just watch. The rallies go on for an absurd number of returns sometimes — it's weirdly hypnotic.

View Receive No.1 →