diff --git a/README.md b/README.md
index 7dfbacb..cd0478e 100644
--- a/README.md
+++ b/README.md
@@ -57,22 +57,30 @@ sudo ln -s $(pwd)/osc /usr/local/bin/osc
 
 ## Configuration
 
-Edit the constants at the top of `src/osc.nim` or `src/osc_braille.nim`:
+Runtime options can be passed via CLI flags:
 
-```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
+```bash
+./osc --palette:amber --decay:0.92 --beam:0.6 --bloom:0.12
+./osc_braille --palette:green --hot:0.8 --warm:0.45 --cool:0.12
+```
 
-  # Phosphor glow thresholds
-  HotGlow = 0.7          # white-hot beam core
-  WarmGlow = 0.4         # bright phosphor
-  CoolGlow = 0.15        # dim persistence trail
+Available options:
 
-  # Palette: green, amber, cyan, blue, white, red
-  Palette = "green"
+| Option | Description | Default |
+|--------|-------------|---------|
+| `-p`, `--palette:NAME` | Palette name | `green` |
+| `-d`, `--decay:FLOAT` | Phosphor persistence per frame | `0.85` |
+| `--beam:FLOAT` | Beam impact intensity | `0.4` |
+| `--bloom:FLOAT` | Horizontal glow spread | `0.08` |
+| `--hot:FLOAT` | White-hot beam core threshold | `0.7` |
+| `--warm:FLOAT` | Bright phosphor threshold | `0.4` |
+| `--cool:FLOAT` | Dim persistence trail threshold | `0.15` |
+
+Show help:
+
+```bash
+./osc --help
+./osc_braille --help
 ```
 
 ### Palettes
diff --git a/src/osc.nim b/src/osc.nim
index e021e21..4ec0a1d 100644
--- a/src/osc.nim
+++ b/src/osc.nim
@@ -1,28 +1,83 @@
 ## Terminal oscilloscope with CRT phosphor physics.
 ## Zero dependencies beyond Nim stdlib + libav (dlopen at runtime).
 
-import os, strutils
+import os, strutils, parseopt
 import posix/termios as ptermios
 from posix import read
 import osc/canvas/[term, effects]
 import osc/[scope, audio]
 
 # ── Configuration ────────────────────────────────────────────────────
-# Edit these to tune the look.
 
-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
+type Config = object
+  decay: float
+  beam: float
+  bloom: float
+  hotGlow: float
+  warmGlow: float
+  coolGlow: float
+  palette: string
 
-  # Phosphor glow thresholds
-  HotGlow = 0.7          # white-hot beam core
-  WarmGlow = 0.4         # bright phosphor
-  CoolGlow = 0.15        # dim persistence trail
+proc defaultConfig(): Config =
+  Config(
+    decay: 0.85,
+    beam: 0.4,
+    bloom: 0.08,
+    hotGlow: 0.7,
+    warmGlow: 0.4,
+    coolGlow: 0.15,
+    palette: "green"
+  )
 
-  # Palette: green, amber, cyan, blue, white, red
-  Palette = "green"
+proc usage() =
+  echo """
+Terminal oscilloscope
+
+Options:
+  -p, --palette:NAME   Palette name, default: green
+  -d, --decay:FLOAT    Phosphor decay, default: 0.85
+      --beam:FLOAT     Beam intensity, default: 0.4
+      --bloom:FLOAT    Bloom intensity, default: 0.08
+      --hot:FLOAT      Hot glow, default: 0.7
+      --warm:FLOAT     Warm glow, default: 0.4
+      --cool:FLOAT     Cool glow, default: 0.15
+  -h, --help           Show this help
+
+Palettes:
+  green, amber, cyan, blue, white, red
+
+Example:
+  ./osc --palette:amber --decay:0.92 --beam:0.6 --bloom:0.12
+"""
+
+proc parseConfig(): Config =
+  result = defaultConfig()
+
+  for kind, key, val in getopt():
+    case kind
+    of cmdLongOption, cmdShortOption:
+      case key
+      of "h", "help":
+        usage()
+        quit 0
+      of "palette", "p":
+        result.palette = val
+      of "decay", "d":
+        result.decay = parseFloat(val)
+      of "beam":
+        result.beam = parseFloat(val)
+      of "bloom":
+        result.bloom = parseFloat(val)
+      of "hot":
+        result.hotGlow = parseFloat(val)
+      of "warm":
+        result.warmGlow = parseFloat(val)
+      of "cool":
+        result.coolGlow = parseFloat(val)
+      else:
+        quit "Unknown option: " & key
+    else:
+      discard
 
 # ── Audio thread via Channel ─────────────────────────────────────────
 
@@ -66,94 +121,171 @@ proc readKey(): char =
 
 # ── Phosphor ─────────────────────────────────────────────────────────
 
-proc plotDot(c: var Canvas, fx, fy: float) =
-  let x = int(fx); let y = int(fy)
-  c.addPixel(x, y, Beam)
-  c.addPixel(x - 1, y, Bloom)
-  c.addPixel(x + 1, y, Bloom)
+proc plotDot(c: var Canvas, fx, fy: float, cfg: Config) =
+  let x = int(fx)
+  let y = int(fy)
 
-proc plotLine(c: var Canvas, x0, y0, x1, y1: float) =
+  c.addPixel(x, y, cfg.beam)
+  c.addPixel(x - 1, y, cfg.bloom)
+  c.addPixel(x + 1, y, cfg.bloom)
+
+proc plotLine(
+  c: var Canvas,
+  x0, y0, x1, y1: float,
+  cfg: Config
+) =
   let steps = max(int(max(abs(x1 - x0), abs(y1 - y0))), 1)
+
   for i in 0..steps:
     let t = i.float / steps.float
-    c.plotDot(x0 + (x1 - x0) * t, y0 + (y1 - y0) * t)
 
-proc renderTrace(c: var Canvas, scope: Scope) =
-  if scope.sampleCount < 2: return
-  let w = c.pixW; let h = c.pixH
-  let cy = h.float / 2.0; let gain = scope.gain
+    c.plotDot(
+      x0 + (x1 - x0) * t,
+      y0 + (y1 - y0) * t,
+      cfg
+    )
+
+proc renderTrace(c: var Canvas, scope: Scope, cfg: Config) =
+  if scope.sampleCount < 2:
+    return
+
+  let w = c.pixW
+  let h = c.pixH
+  let cy = h.float / 2.0
+  let gain = scope.gain
 
   case scope.mode
   of ModeYT:
     let visible = max(int(scope.sampleCount.float / scope.timeDiv), 2)
-    var px, py: float; var first = true
+
+    var px, py: float
+    var first = true
+
     for col in 0..<w:
       let s = min((col * visible) div w, scope.sampleCount - 1)
-      let x = col.float; let y = cy - scope.samplesL[s] * gain * cy * 0.5
-      if first: c.plotDot(x, y) else: c.plotLine(px, py, x, y)
-      first = false; px = x; py = y
+      let x = col.float
+      let y = cy - scope.samplesL[s] * gain * cy * 0.5
+
+      if first:
+        c.plotDot(x, y, cfg)
+      else:
+        c.plotLine(px, py, x, y, cfg)
+
+      first = false
+      px = x
+      py = y
+
   of ModeXY:
-    var px, py: float; var first = true
+    var px, py: float
+    var first = true
+
     let step = max(scope.sampleCount div 1024, 1)
+
     for i in countup(0, scope.sampleCount - 1, step):
       let x = (1.0 + scope.samplesL[i] * gain * 0.5) * w.float / 2.0
       let y = (1.0 - scope.samplesR[i] * gain * 0.5) * h.float / 2.0
-      if first: c.plotDot(x, y) else: c.plotLine(px, py, x, y)
-      first = false; px = x; py = y
+
+      if first:
+        c.plotDot(x, y, cfg)
+      else:
+        c.plotLine(px, py, x, y, cfg)
+
+      first = false
+      px = x
+      py = y
 
 # ── Main ─────────────────────────────────────────────────────────────
 
 proc main() =
+  let cfg = parseConfig()
+
   initTerm()
   setRawMode()
 
-  var w = termWidth(); var h = termHeight()
-  var c = newCanvas(w, h, Palette, [HotGlow, WarmGlow, CoolGlow])
+  var w = termWidth()
+  var h = termHeight()
+
+  var c = newCanvas(
+    w,
+    h,
+    cfg.palette,
+    [cfg.hotGlow, cfg.warmGlow, cfg.coolGlow]
+  )
+
   crtTurnOn(c)
+
   var scope = initScope(w, h)
   var aud = startAudio()
   var running = true
 
   audioChan.open()
   audioRunning = true
+
   var aThread: Thread[ptr AudioCapture]
   createThread(aThread, audioThread, addr aud)
 
   while running:
-    let nw = termWidth(); let nh = termHeight()
+    let nw = termWidth()
+    let nh = termHeight()
+
     if nw != w or nh != h:
-      w = nw; h = nh; c.resize(w, h); scope.resize(w, h)
+      w = nw
+      h = nh
+      c.resize(w, h)
+      scope.resize(w, h)
 
     let got = audioChan.tryRecv()
+
     if got.dataAvailable:
       scope.sampleCount = got.msg.count
+
       for i in 0..<got.msg.count:
         scope.samplesL[i] = got.msg.samples[i][0]
         scope.samplesR[i] = got.msg.samples[i][1]
 
-    c.decayPixels(Decay)
-    c.renderTrace(scope)
+    c.decayPixels(cfg.decay)
+    c.renderTrace(scope, cfg)
+
+    let hud =
+      " " &
+      (if scope.mode == ModeYT: "Y-T" else: "X-Y") &
+      " G:" &
+      scope.gain.formatFloat(ffDecimal, 1) &
+      " "
 
-    let hud = " " & (if scope.mode == ModeYT: "Y-T" else: "X-Y") &
-              " G:" & scope.gain.formatFloat(ffDecimal, 1) & " "
     let help = " m:mode +/-:gain [/]:time q:quit "
-    c.flush([(1, 0, tNormal, hud),
-             (w - help.len - 1, h - 1, tDim, help)])
+
+    c.flush([
+      (1, 0, tNormal, hud),
+      (w - help.len - 1, h - 1, tDim, help)
+    ])
 
     sleep(16)
 
     case readKey()
-    of 'q', '\x1b': running = false
-    of 'm': scope.mode = if scope.mode == ModeYT: ModeXY else: ModeYT
-    of '+', '=': scope.gain = min(scope.gain * 1.3, 20.0)
-    of '-': scope.gain = max(scope.gain / 1.3, 0.5)
-    of ']': scope.timeDiv = min(scope.timeDiv * 1.5, 16.0)
-    of '[': scope.timeDiv = max(scope.timeDiv / 1.5, 0.25)
-    else: discard
+    of 'q', '\x1b':
+      running = false
+    of 'm':
+      scope.mode =
+        if scope.mode == ModeYT:
+          ModeXY
+        else:
+          ModeYT
+    of '+', '=':
+      scope.gain = min(scope.gain * 1.3, 20.0)
+    of '-':
+      scope.gain = max(scope.gain / 1.3, 0.5)
+    of ']':
+      scope.timeDiv = min(scope.timeDiv * 1.5, 16.0)
+    of '[':
+      scope.timeDiv = max(scope.timeDiv / 1.5, 0.25)
+    else:
+      discard
 
   audioRunning = false
   joinThread(aThread)
   audioChan.close()
+
   aud.stop()
   crtTurnOff(c)
   restoreMode()
diff --git a/src/osc_braille.nim b/src/osc_braille.nim
index 28714f0..5f437f9 100644
--- a/src/osc_braille.nim
+++ b/src/osc_braille.nim
@@ -1,6 +1,6 @@
 ## Terminal oscilloscope — braille dot rendering (4× resolution).
 
-import os, strutils
+import os, strutils, parseopt
 import posix/termios as ptermios
 from posix import read
 import osc/canvas/[braille, term, effects]
@@ -8,14 +8,72 @@ import osc/[scope, audio]
 
 # ── Configuration ────────────────────────────────────────────────────
 
-const
-  Decay = 0.85
-  Beam = 0.4
-  Bloom = 0.08
-  HotGlow = 0.7
-  WarmGlow = 0.4
-  CoolGlow = 0.15
-  Palette = "green"
+type Config = object
+  decay: float
+  beam: float
+  bloom: float
+  hotGlow: float
+  warmGlow: float
+  coolGlow: float
+  palette: string
+
+proc defaultConfig(): Config =
+  Config(
+    decay: 0.85,
+    beam: 0.4,
+    bloom: 0.08,
+    hotGlow: 0.7,
+    warmGlow: 0.4,
+    coolGlow: 0.15,
+    palette: "green"
+  )
+
+proc usage() =
+  echo """
+Terminal oscilloscope
+
+Options:
+  -p, --palette:NAME   Palette name, default: green
+  -d, --decay:FLOAT    Phosphor decay, default: 0.85
+      --beam:FLOAT     Beam intensity, default: 0.4
+      --bloom:FLOAT    Bloom intensity, default: 0.08
+      --hot:FLOAT      Hot glow, default: 0.7
+      --warm:FLOAT     Warm glow, default: 0.4
+      --cool:FLOAT     Cool glow, default: 0.15
+  -h, --help           Show this help
+
+Example:
+  ./osc_braille --palette:amber --decay:0.92 --beam:0.6 --bloom:0.12
+"""
+
+proc parseConfig(): Config =
+  result = defaultConfig()
+
+  for kind, key, val in getopt():
+    case kind
+    of cmdLongOption, cmdShortOption:
+      case key
+      of "h", "help":
+        usage()
+        quit 0
+      of "palette", "p":
+        result.palette = val
+      of "decay", "d":
+        result.decay = parseFloat(val)
+      of "beam":
+        result.beam = parseFloat(val)
+      of "bloom":
+        result.bloom = parseFloat(val)
+      of "hot":
+        result.hotGlow = parseFloat(val)
+      of "warm":
+        result.warmGlow = parseFloat(val)
+      of "cool":
+        result.coolGlow = parseFloat(val)
+      else:
+        quit "Unknown option: " & key
+    else:
+      discard
 
 # ── Audio thread ─────────────────────────────────────────────────────
 
@@ -59,95 +117,173 @@ proc readKey(): char =
 
 # ── Phosphor ─────────────────────────────────────────────────────────
 
-proc plotDot(c: var BrailleCanvas, fx, fy: float) =
-  let x = int(fx); let y = int(fy)
-  c.addPixel(x, y, Beam)
-  c.addPixel(x - 1, y, Bloom)
-  c.addPixel(x + 1, y, Bloom)
+proc plotDot(c: var BrailleCanvas, fx, fy: float, cfg: Config) =
+  let x = int(fx)
+  let y = int(fy)
+  c.addPixel(x, y, cfg.beam)
+  c.addPixel(x - 1, y, cfg.bloom)
+  c.addPixel(x + 1, y, cfg.bloom)
 
-proc plotLine(c: var BrailleCanvas, x0, y0, x1, y1: float) =
+proc plotLine(
+  c: var BrailleCanvas,
+  x0, y0, x1, y1: float,
+  cfg: Config
+) =
   let steps = max(int(max(abs(x1 - x0), abs(y1 - y0))), 1)
   for i in 0..steps:
     let t = i.float / steps.float
-    c.plotDot(x0 + (x1 - x0) * t, y0 + (y1 - y0) * t)
+    c.plotDot(
+      x0 + (x1 - x0) * t,
+      y0 + (y1 - y0) * t,
+      cfg
+    )
 
-proc renderTrace(c: var BrailleCanvas, scope: Scope) =
-  if scope.sampleCount < 2: return
-  let w = c.pixW; let h = c.pixH
-  let cy = h.float / 2.0; let gain = scope.gain
+proc renderTrace(c: var BrailleCanvas, scope: Scope, cfg: Config) =
+  if scope.sampleCount < 2:
+    return
+
+  let w = c.pixW
+  let h = c.pixH
+  let cy = h.float / 2.0
+  let gain = scope.gain
 
   case scope.mode
   of ModeYT:
     let visible = max(int(scope.sampleCount.float / scope.timeDiv), 2)
-    var px, py: float; var first = true
+    var px, py: float
+    var first = true
+
     for col in 0..<w:
       let s = min((col * visible) div w, scope.sampleCount - 1)
-      let x = col.float; let y = cy - scope.samplesL[s] * gain * cy * 0.5
-      if first: c.plotDot(x, y) else: c.plotLine(px, py, x, y)
-      first = false; px = x; py = y
+      let x = col.float
+      let y = cy - scope.samplesL[s] * gain * cy * 0.5
+
+      if first:
+        c.plotDot(x, y, cfg)
+      else:
+        c.plotLine(px, py, x, y, cfg)
+
+      first = false
+      px = x
+      py = y
+
   of ModeXY:
-    var px, py: float; var first = true
+    var px, py: float
+    var first = true
     let step = max(scope.sampleCount div 1024, 1)
+
     for i in countup(0, scope.sampleCount - 1, step):
       let x = (1.0 + scope.samplesL[i] * gain * 0.5) * w.float / 2.0
       let y = (1.0 - scope.samplesR[i] * gain * 0.5) * h.float / 2.0
-      if first: c.plotDot(x, y) else: c.plotLine(px, py, x, y)
-      first = false; px = x; py = y
+
+      if first:
+        c.plotDot(x, y, cfg)
+      else:
+        c.plotLine(px, py, x, y, cfg)
+
+      first = false
+      px = x
+      py = y
 
 # ── Main ─────────────────────────────────────────────────────────────
 
 proc main() =
+  let cfg = parseConfig()
+
   initTerm()
   setRawMode()
 
-  var w = termWidth(); var h = termHeight()
-  var hb = newCanvas(w, h, Palette, [HotGlow, WarmGlow, CoolGlow])
+  var w = termWidth()
+  var h = termHeight()
+
+  var hb = newCanvas(
+    w,
+    h,
+    cfg.palette,
+    [cfg.hotGlow, cfg.warmGlow, cfg.coolGlow]
+  )
+
   crtTurnOn(hb)
-  var c = newBrailleCanvas(w, h, Palette, [HotGlow, WarmGlow, CoolGlow])
+
+  var c = newBrailleCanvas(
+    w,
+    h,
+    cfg.palette,
+    [cfg.hotGlow, cfg.warmGlow, cfg.coolGlow]
+  )
+
   var scope = initScope(w, h)
   var aud = startAudio()
   var running = true
 
   audioChan.open()
   audioRunning = true
+
   var aThread: Thread[ptr AudioCapture]
   createThread(aThread, audioThread, addr aud)
 
   while running:
-    let nw = termWidth(); let nh = termHeight()
+    let nw = termWidth()
+    let nh = termHeight()
+
     if nw != w or nh != h:
-      w = nw; h = nh; c.resize(w, h); scope.resize(w, h)
+      w = nw
+      h = nh
+      c.resize(w, h)
+      scope.resize(w, h)
 
     let got = audioChan.tryRecv()
+
     if got.dataAvailable:
       scope.sampleCount = got.msg.count
+
       for i in 0..<got.msg.count:
         scope.samplesL[i] = got.msg.samples[i][0]
         scope.samplesR[i] = got.msg.samples[i][1]
 
-    c.decayPixels(Decay)
-    c.renderTrace(scope)
+    c.decayPixels(cfg.decay)
+    c.renderTrace(scope, cfg)
+
+    let hud =
+      " " &
+      (if scope.mode == ModeYT: "Y-T" else: "X-Y") &
+      " G:" &
+      scope.gain.formatFloat(ffDecimal, 1) &
+      " "
 
-    let hud = " " & (if scope.mode == ModeYT: "Y-T" else: "X-Y") &
-              " G:" & scope.gain.formatFloat(ffDecimal, 1) & " "
     let help = " m:mode +/-:gain [/]:time q:quit "
-    c.flush([(1, 0, tNormal, hud),
-             (w - help.len - 1, h - 1, tDim, help)])
+
+    c.flush([
+      (1, 0, tNormal, hud),
+      (w - help.len - 1, h - 1, tDim, help)
+    ])
 
     sleep(16)
 
     case readKey()
-    of 'q', '\x1b': running = false
-    of 'm': scope.mode = if scope.mode == ModeYT: ModeXY else: ModeYT
-    of '+', '=': scope.gain = min(scope.gain * 1.3, 20.0)
-    of '-': scope.gain = max(scope.gain / 1.3, 0.5)
-    of ']': scope.timeDiv = min(scope.timeDiv * 1.5, 16.0)
-    of '[': scope.timeDiv = max(scope.timeDiv / 1.5, 0.25)
-    else: discard
+    of 'q', '\x1b':
+      running = false
+    of 'm':
+      scope.mode =
+        if scope.mode == ModeYT:
+          ModeXY
+        else:
+          ModeYT
+    of '+', '=':
+      scope.gain = min(scope.gain * 1.3, 20.0)
+    of '-':
+      scope.gain = max(scope.gain / 1.3, 0.5)
+    of ']':
+      scope.timeDiv = min(scope.timeDiv * 1.5, 16.0)
+    of '[':
+      scope.timeDiv = max(scope.timeDiv / 1.5, 0.25)
+    else:
+      discard
 
   audioRunning = false
   joinThread(aThread)
   audioChan.close()
+
   aud.stop()
   crtTurnOff(hb)
   restoreMode()