Research Paddle Bounce

How paddle-and-ball games actually compute the post-bounce direction. Background reading for 01-prototype/tech/03-paddle-bounce.md.

Summary

The dominant pattern in paddle-and-ball games is to replace the incoming angle, not reflect it. The post-bounce direction is computed from where the ball touched the paddle (and in modern racket games, from player input at contact). Incoming angle is discarded. Pure angle-of-incidence reflection is described in the source material as "the most simplistic Pong" and was the design Atari moved away from in 1972 because it played as "too boring."

Classic Pong (1972, Atari)

Allan Alcorn divided the paddle into eight segments. Centre segments returned the ball at 90° to the paddle; outer segments at smaller angles. There was no continuous function and no preservation of incoming angle: the segment alone picked the output direction. Sources call this "completely arbitrary" but functional, designed to add strategic depth without floating-point math the hardware did not have [^pong-wiki] [^cornell-pong] [^bespoke-pong].

Breakout / Arkanoid family

Every reference describes the same pattern: compute hit offset (ball.x − paddle.x), normalise to roughly [-1, +1], use that as the new x-component, set y-component to a fixed positive value, normalise, multiply by speed. Incoming angle is discarded. Some variants additionally mix in paddle velocity for "english" [^breakernoid] [^smiling-cat] [^gamedev-breakout].

Modern paddle / racket games

Three patterns surveyed, all of which discard pure angle-of-incidence reflection:

• Wii Sports / Switch Sports tennis: direction is a function of swing timing, not paddle geometry. Early swing on forehand goes cross-court, late swing goes down-the-line. Wrist angle reads spin [^wii-tennis-sw] [^wii-tennis-wiki].
• Lethal League / Lethal League Blaze: "neutral swing" releases the ball at one of three player-selected angles (Up / Neutral / Down) at the moment the swing animation ends. Incoming angle fully replaced [^lethal-league].
• Windjammers: holding a direction at contact angles the disc diagonally; per-character "attack angles" the disc differently [^script-routine].

Every modern racket-feel game gives the player intent at the contact moment, and that intent picks the new direction.

Canonical tutorial pattern

All most-referenced 2D-physics tutorials replace the incoming direction with a hard-coded y-sign:

• MDN / Phaser Breakout: ball.body.velocity.x = -5 * (paddle.x - ball.x) [^mdn-phaser].
• CS50 Breakout (Lua/LÖVE): ball.dx = ±50 + ±8 * |paddle.center - ball.x|. Additive with a non-zero floor, gated by paddle movement direction [^cs50-breakout].
• StudyPlan SDL2 Breakout: offset normalised to [-1, +1] becomes x, y forced to a positive constant [^studyplan-sdl2].
• MonoGame Breakernoid: same shape, with clamping to avoid near-vertical bounces [^breakernoid].

Common refinements in the tutorials: clamp away from horizontal-near-vertical, mix paddle velocity for english, renormalise to constant ball speed after the math.

On the semantic question

No Steve Swink or Game Maker's Toolkit piece lands cleanly on "preserve incoming angle vs replace it" for racket games, but the surrounding material is consistent:

• Pure angle-of-incidence reflection is treated as a baseline to improve on, not a target feel [^gamedev-pong].
• The shipped 1972 Pong intentionally departed from pure reflection because Alcorn felt the game was "too boring" without the 8-segment table [^pong-wiki].
• Tutorials explicitly justify offset-overwrite as "where the ball hits the paddle has a strong effect on direction... this is what gives players control" [^breakernoid] [^studyplan-sdl2].
• Real tennis physics: perpendicular-to-racket velocity is roughly preserved, but the parallel-to-racket component reverses, and string friction plus spin make the bounce deviate significantly from incidence. Even the realistic reference does not behave like a mirror [^tennis-physics].

The genre convention, taught in every tutorial and shipped in every reference game found, is that contact offset or player input at contact picks the post-bounce direction and incoming angle is largely or wholly discarded.

Sources

[^pong-wiki]: Pong, Wikipedia. Retrieved 2026-05-13. [^cornell-pong]: Atari's Pong Reimagined, Cornell ECE4760. Retrieved 2026-05-13. [^bespoke-pong]: Pong, Bespoke Arcades. Retrieved 2026-05-13. [^breakernoid]: Building Breakernoid in MonoGame, InformIT. Retrieved 2026-05-13. [^smiling-cat]: Physics for a Block Breaker Game, Smiling Cat. Retrieved 2026-05-13. [^gamedev-breakout]: Breakout-bounce thread, GameDev.net. Retrieved 2026-05-13. [^wii-tennis-sw]: Wii Sports Tennis, StrategyWiki. Retrieved 2026-05-13. [^wii-tennis-wiki]: Tennis, Wii Sports Wiki. Retrieved 2026-05-13. [^lethal-league]: Gameplay/Mechanics, Lethal League Wiki. Retrieved 2026-05-13. [^script-routine]: Sports Game Triple Play: Pong → Windjammers → Lethal League, Script Routine. Retrieved 2026-05-13. [^mdn-phaser]: Randomizing gameplay, MDN Phaser Breakout tutorial. Retrieved 2026-05-13. [^cs50-breakout]: Breakout notes, CS50G. Retrieved 2026-05-13. [^studyplan-sdl2]: Breakout Paddle Physics, StudyPlan SDL2. Retrieved 2026-05-13. [^gamedev-pong]: Best PONG bounce method, GameDev.net. Retrieved 2026-05-13. [^tennis-physics]: Physics of Tennis, Tennis Without Talent. Retrieved 2026-05-13.