diff --git a/docs/mainframe-design.md b/docs/mainframe-design.md
index dc9b567..83db717 100644
--- a/docs/mainframe-design.md
+++ b/docs/mainframe-design.md
@@ -7,29 +7,34 @@ The components of a Mark I are:
 - a CG 103 Print-Key-Punch
 - a CG 104 Matrix Display
 
-### Console
+### Operator console
 
 <mark>TBC TBC TBC</mark>
 
-The console is equipped with:
+## Basic controls
 
-- Power switch
-- Load button
-- Run button
-- Run Single Step button
-- Halt button
-- Memory Read button
-- Memory Read Next button
-- Memory Write button
-- Memory Write Next button
+- Power
+- Load
+- Run
+- Halt
 - 4 Sense Switches
 
+## Status lights
+
 - 8 Accumulator lights
 - 8 Address lights
 - 8 Data lights
 - 8 Instruction Pointer lights (<mark>review IP size?</mark>)
 - 8 Status Register lights
 
+## Debugging controls
+
+- Run Single Step
+- Memory Read
+- Memory Read Next
+- Memory Write
+- Memory Write Next
+
 ## IO programming
 
 Only one input or output device can be accessed at a time.