Add #114 Audio Terrain: sound visualizer landscape (fills gap)

Multi-frequency terrain: bass creates rolling hills, mids form ridges,
highs add fine detail. Beat pulses boost amplitude. Fills the 'sound
visualization' category gap identified by the quality audit (was 0).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: danlex

README.md

@@ -1,19 +1,19 @@
 # Particles
 
 [![GitHub Pages](https://img.shields.io/badge/Live%20Demo-danlex.github.io%2Fparticles-blue?style=flat-square)](https://danlex.github.io/particles/)
-[![Animations](https://img.shields.io/badge/Animations-113-brightgreen?style=flat-square)](https://danlex.github.io/particles/)
+[![Animations](https://img.shields.io/badge/Animations-114-brightgreen?style=flat-square)](https://danlex.github.io/particles/)
 [![Three.js](https://img.shields.io/badge/Three.js-r160-orange?style=flat-square)](https://threejs.org/)
 [![License: MIT](https://img.shields.io/badge/License-MIT-yellow?style=flat-square)](LICENSE)
 
-A gallery of **113 real-time, interactive GPU particle animations**. Each runs **65,536 particles** entirely on the GPU using [Three.js](https://threejs.org/) r160 and `GPUComputationRenderer`.
+A gallery of **114 real-time, interactive GPU particle animations**. Each runs **65,536 particles** entirely on the GPU using [Three.js](https://threejs.org/) r160 and `GPUComputationRenderer`.
 
 **[View Live Gallery](https://danlex.github.io/particles/)**
 
 ---
 
 ## Features
 
-- **113 unique animations** across 13 categories
+- **114 unique animations** across 13 categories
 - **65,536 particles** per animation (256x256 GPU compute texture)
 - **Mouse interaction** — particles react to your cursor in every animation
 - **Real-time controls** — Speed, Bloom, Size, Hue sliders + zoom buttons