update control layer

README.md

@@ -11,7 +11,19 @@ Features:
 - brackets and punctuation on default layer
 - Symbol layer with numpad
 - function layer with vim navigation
-- home row mod?
-- thumb cluster with control keys and tab dances
+- hold character to use `Ctrl` layer
+- character combos to switch tabs, windows, and wrokspaces
+- thumb cluster for modifiers and layer switching
 
 ![](keymap.svg)
+
+## Layers
+
+| L1  | L2            | L3           |
+| --- | ------------- | ------------ |
+|     | control layer | symbol layer |
+
+- switch layers using left thumb cluster
+- hold key to activate layer temporarily (e.g. just one symbol)
+- double tap key to activate layer persistently (e.g. navigation for a while), removing muscle strain.
+- Alternatively, holding a character key will yield its `ctrl` variant, e.g. hold `c` to copy, removing the need to hold the ctrl modifier