diff --git a/register_notes b/register_notes
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index 0000000..4c8273e
--- /dev/null
+++ b/register_notes
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+
+
+$2100 - screen on/off + brightness
+
+$2105 - screen format register, changes size of tiles
+
+
+$2121 - stores the index into CGRAM to write a color value via $2122
+
+
+$2122 - write a 2-byte SNES color value to the CGRAM. this auto-increments after writing,
+which is why $2121 needs to be written to reset this. it's common to write `stz $2121`
+
+