3 files changed, 15 insertions, 0 deletions
diff --git a/nandgame/comb_mem.sv b/nandgame/comb_mem.sv
index bbfdcd0..dcda331 100644
--- a/nandgame/comb_mem.sv
+++ b/nandgame/comb_mem.sv
@@ -1,3 +1,7 @@
+// nandgame "combined memory"
+// contains registers A, D and *A result
+// located in memory.
+
 `timescale 1us/1us
 
 `include "../my_mem.v"
diff --git a/nandgame/logic_unit.sv b/nandgame/logic_unit.sv
index 32b9691..93cb399 100644
--- a/nandgame/logic_unit.sv
+++ b/nandgame/logic_unit.sv
@@ -14,11 +14,14 @@ module logic_unit #(
   output logic [(DATA_WIDTH-1):0] RES
 );
 
+// learning: instead of this nested ternary...
 // assign RES = operation == LOGIC_AND ? (X & Y) : 
 //               operation == LOGIC_OR ? (X | Y) :
 //               operation == LOGIC_XOR ? (X ^ Y) :
 //               operation == LOGIC_NEGT ? (~X) : 0;
 
+// ... you can do this:
+
 always_comb begin
     case (operation)
         LOGIC_AND: RES = X & Y;
diff --git a/nandgame/nandgame_types.v b/nandgame/nandgame_types.v
index f7273da..2558383 100644
--- a/nandgame/nandgame_types.v
+++ b/nandgame/nandgame_types.v
@@ -1,3 +1,11 @@
+// common types for nandgame
+
+// learning:
+// you need an include guard if you include files
+// in multiple files.
+// otherwise, iverilog and verilator will
+// complain when loading the test bench and the
+// corresponding uut.
 `ifndef NANDGAME_TYPES_SV
 `define NANDGAME_TYPES_SV