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+# Dev notes — 2023-08-07
+
+## Keypad
+
+An actual hexadecimal layout:
+
+```
+0 1 2 3
+4 5 6 7
+8 9 A B
+C D E F
+```
+
+Another:
+
+```
+1 2 3 A
+4 5 6 B
+7 8 9 C
+0 F E D
+```
+
+The conventional layout for cheap hardware:
+
+```
+1 2 3 A
+4 5 6 B
+7 8 9 C
+* 0 # D
+```
+
+Kim-1:
+
+```
+    GO  ST  RS
+AD  DA  PC  +
+C   D   E   F
+8   9   A   B
+4   5   6   7
+0   1   2   3
+```
+
+COSMAC VIP/CHIP-8:
+
+```
+1 2 3 C
+4 5 6 D
+7 8 9 E
+A 0 B F
+```
+
+CHIP-8 to QWERTY mapping:
+
+```
+1 2 3 4
+Q W E R
+A S D F
+Z X C V
+```
+
+## Turtle graphics
+
+- yesterday Elizabeth had the great idea to create a turtle robot to go with the paper computer
+- a minimal LOGO would be a fantastic (if challenging) program to write for the computer
+  - it could use the hex keypad:
+    - using CHIP-8 layout...
+    - A key: mode toggle
+    - mode 1: numeric
+    - mode 2: commands (tokens?)... something like this:
+      - `F` - mode toggle
+      - `2` - forward
+      - `4` - left
+      - `6` - right
+      - `0` - reverse
+      - `5` - turn
+      - `1` - pen up
+      - `C` - pen down
+
+## Dot-matrix display
+
+- Maybe try 5x5, like the micro:bit?
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