diff --git a/README.md b/README.md
index 0645edc..f21dd76 100644
--- a/README.md
+++ b/README.md
@@ -48,7 +48,8 @@ Add or symlink ROMs to `roms/` at your leisure. Note that they must end in
 `.gg` or `.bin` to be auto-detected.
 
 Add `--fullscreen` (`-f`) to enable fullscreen mode, or `--scale <n>`
-(`-s <n>`) to scale the game screen by an integer factor.
+(`-s <n>`) to scale the game screen by an integer factor in windowed mode (this
+only sets the starting configuration; the window should be resizeable).
 
 Add `--debug` (`-g`) to show logging information while running. Pass it twice
 (`-gg`) to show more detailed logs, including an emulator trace.
@@ -56,6 +57,19 @@ Add `--debug` (`-g`) to show logging information while running. Pass it twice
 `./crater -h` gives (fairly basic) command-line usage, and `./crater -v` gives
 the current version.
 
+### Key mapping
+
+Custom key mappings are not supported. There are two primary configurations I
+like:
+
+- `Return`/`Esc` for `Start`; `WASD` for D-pad; `.` for `1`/left trigger;
+  `/` for `2`/right trigger
+
+- `Return`/`Esc` for `Start`; arrow keys for D-pad; `Z` for `1`/left trigger;
+  `X` for `2`/right trigger
+
+You can switch between them freely.
+
 ### Assembler/Disassembler
 
 crater has built-in support for converting Z80 assembly into ROM images, as
diff --git a/src/emulator.c b/src/emulator.c
index 39b1098..f623b6b 100644
--- a/src/emulator.c
+++ b/src/emulator.c
@@ -105,10 +105,16 @@ static void handle_keypress(GameGear *gg, SDL_Keycode key, bool state)
         case SDLK_d:
             button = BUTTON_RIGHT;     break;
         case SDLK_j:
+        case SDLK_z:
+        case SDLK_PERIOD:
             button = BUTTON_TRIGGER_1; break;
         case SDLK_k:
+        case SDLK_x:
+        case SDLK_SLASH:
             button = BUTTON_TRIGGER_2; break;
         case SDLK_RETURN:
+        case SDLK_RETURN2:
+        case SDLK_ESCAPE:
             button = BUTTON_START;     break;
         default:
             return;