Sorry for this one: a Birdy Flap postmortem

Every developer, at some point, builds a Flappy Bird clone. It's not a choice, it's a life stage — like a first apartment or a regrettable haircut. Birdy Flap is mine. The card on the homepage says "Sorry for this one" and I stand by the apology. But since it exists anyway, here's what building the world's most-cloned game actually teaches you.

Why is a one-button game so hard to build well?

Because there is nowhere to hide. A game with one input and three rules lives or dies entirely on feel, and feel is three numbers: gravity, flap impulse, and scroll speed. Get them right and the game is "one more try" for an hour. Get gravity 10% too high and it's "this is broken" in four seconds. I changed those three constants more often than everything else in the code combined.

The gravity problem

Real-ish physics (velocity += gravity × dt; position += velocity × dt) feels floaty and terrible for this genre. The original Flappy Bird uses comically exaggerated gravity with a sharp, instant flap impulse — the bird is less "bird" and more "brick with anxiety". The lesson generalises: games simulate feelings, not physics. Racing games fake grip, shooters fake recoil, and flappy games fake a bird that responds to guilt.

Why do people keep playing something so annoying?

The death loop is engineered, whether the developer knows it or not:

• Deaths are always your fault. The pipes never move; the physics never changes. No RNG to blame.
• Restarting is instant. Zero loading, zero menus. The next attempt starts before the shame lands.
• The score is one integer. Your entire self-worth compresses into "7", and your friend has "11".

That's the whole psychological machine. It's the same loop that makes Wordle and speedrunning work, in its smallest possible form.

What I'd tell anyone building one

1. Tune with real hands on a real phone. The same constants feel different on a 60 Hz monitor with a keyboard.
2. Make the hitbox smaller than the sprite. Players think "that was close"; the game agrees generously.
3. Kill the bird on the ceiling too, or the optimal strategy becomes "hug the top", and optimal strategies are boring.
4. Ship it. It's a rite of passage, not a product.

Should you play it?

No. But you will. It's right here, it loads instantly, it costs nothing, and it doesn't track you — the purest possible distillation of wasting time. Sorry for this one.