diff --git a/README.md b/README.md
index 711ee7c..f4de4c7 100644
--- a/README.md
+++ b/README.md
@@ -110,6 +110,8 @@ portability, only backend, avoiding dependencies
 
 how to port to new platform, frontend, configs in files
 
+All global identifiers of the game code start with the prefix `SFG_` (meaning *suckless FPS game*).
+
 The **engine** -- raycastlib -- works on the principle of **raycasting** on a square grid and handles the rendering of the 3D environment (minus sprites). There is a copy of raycastlib in this repository but I maintain raycastlib as a separate project in a different repository, which you can see for more details about it. For us, the important functions interfacing with the engine are e.g. `SFG_floorHeightAt`, `SFG_ceilingHeightAt` (functions the engine uses to retirieve floor and ceiling height) and `SFG_pixelFunc` (function the engine uses to write pixels to the screen during rendering, which in turn uses each platform's specific `SFG_setPixel`).
 
 integer math
diff --git a/TODO.txt b/TODO.txt
index a4810a1..e11ae22 100644
--- a/TODO.txt
+++ b/TODO.txt
@@ -5,8 +5,10 @@ general:
   setting)
 - try to remove the debug flag (-g1) from compiler and see if it decreases size
 - port to GB Meta
-- add enemy moving/dying sound
-- sounds (music?)
+- music:
+  Probably just one long music track playing over and over -- KISS. The frontend
+  could have a callback function play_music_bar(n) which would be called by the
+  backend, the music track would be in sounds.h.
 - level 2D map (with revealing, bitmap), special key for quick displaying map
 - save/load (optional):
   When a level is finished, the state at the beginning of the next one (health,
@@ -147,9 +149,11 @@ done:
 - try to compress images: store images as 4 bits per pixel + 16 color palette
   (subset of the 256 color palette), check if performance stays ok
 - custom font
-- make barrels explode.
+- make barrels explode
 - enemies
 - weapons
+- sounds
+- add enemy moving/dying sound
 - create tables for monster and weapon stats in constants.h and read from that
   instead of cheking with ifs
 - check if monsters are hit by bullets from completely up close