Replace illwill with custom canvas — zero dependencies

- Custom terminal canvas: one buffer, one write() per frame
- Threaded audio via Nim channels (20fps → 60fps)
- 6 phosphor palettes (green, amber, cyan, blue, white, red)
- All tuning constants at top of osc.nim
- No illwill dependency, binary 352KB → 200KB
- CRT effects use same palette as trace

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

README.md

@@ -1,6 +1,6 @@
 # terminal-oscilloscope
 
-A terminal-based oscilloscope with CRT phosphor physics, written in Nim using [illwill](https://github.com/johnnovak/illwill).
+A terminal-based oscilloscope with CRT phosphor physics, written in Nim. Zero dependencies — 200KB binary, just libc.
 
 ![demo](demo.gif)
 
@@ -10,7 +10,9 @@ A terminal-based oscilloscope with CRT phosphor physics, written in Nim using [i
 - **Y-T and X-Y modes** — time-domain waveform or Lissajous figures
 - **Phosphor persistence** — beam bloom, decay trails, intensity-based shading
 - **Half-block rendering** — 2x vertical resolution using Unicode `▀▄█` characters
-- **Live audio capture** — direct libav bindings via dlopen, zero dependencies
+- **Live audio capture** — direct libav bindings via dlopen, zero install
+- **Threaded audio** — 60fps rendering, audio capture on separate thread
+- **6 CRT phosphor palettes** — green, amber, cyan, blue, white, red
 
 ## Install
 
@@ -19,7 +21,7 @@ Requires [Nim](https://nim-lang.org/) 2.x.
 ```bash
 git clone https://github.com/rolandnsharp/terminal-oscilloscope.git
 cd terminal-oscilloscope
-nimble build
+nim c -d:release --threads:on -o:osc src/osc.nim
 ./osc
 ```
 
@@ -32,6 +34,37 @@ nimble build
 | `]` / `[` | Zoom in / out time axis |
 | `q` | Quit (with CRT shutdown effect) |
 
+## Configuration
+
+Edit the constants at the top of `src/osc.nim`:
+
+```nim
+const
+  # Phosphor physics
+  Decay = 0.85           # persistence per frame (0.0–1.0)
+  Beam = 0.4             # intensity at beam impact
+  Bloom = 0.08           # horizontal glow spread
+
+  # Phosphor glow thresholds
+  HotGlow = 0.7          # white-hot beam core
+  WarmGlow = 0.4         # bright phosphor
+  CoolGlow = 0.15        # dim persistence trail
+
+  # Palette: green, amber, cyan, blue, white, red
+  Palette = "green"
+```
+
+### Palettes
+
+| Name | Phosphor | Look |
+|------|----------|------|
+| `green` | P31 | classic oscilloscope |
+| `amber` | P12 | warm retro terminal |
+| `cyan` | P7 | Tektronix blue-green |
+| `blue` | P11 | cool/modern |
+| `white` | P4 | TV phosphor |
+| `red` | P22-R | radar display |
+
 ## Audio
 
 Captures system audio by opening the PulseAudio/PipeWire monitor of your default output sink directly via libavformat and libavdevice. Libraries are loaded at runtime with `dlopen` — no dev packages, no subprocess, no extra dependencies.