decrement white score when shooting

README.md

 
 ## Getting Started
 
-You need the [GBDK-2020](https://gbdk.org/docs/api/docs_getting_started.html) to build the ROM and [Gearboy](https://github.com/drhelius/Gearboy) to emulate it comfortably.
+You need the [GBDK-2020](https://gbdk.org/docs/api/docs_getting_started.html) to build the ROM and [Gearboy](https://github.com/drhelius/Gearboy), [SameBoy](https://sameboy.github.io/), [Emulicious](https://emulicious.net/) or [BGB](https://bgb.bircd.org/) to emulate it comfortably.
 Then just build a debug version and run it in the emulator, with debug symbols already loaded.
 
     make run
+    make sgb_run
+    make bgb_run
+
+Use SameBoy to test out the SGB border feature.
+Also see below for symbolic debugging with Emulicious.
 
 For the release build, simply add `GBDK_RELEASE=1` to your make invocation after running `make clean`.
 
     make clean
     make GBDK_RELEASE=1 run
 
+You can also directly write to a flashcart using `flashgbx` with `make flash`.
+
 ## IDE Integration
 
 I'm using [https://kate-editor.org/] which supports VSCode-style LSP and debugging with integrated plugins.

docs/index.html

                 <tr><td>Select (V)</td><td>About</td></tr>
             </table>
             <p>Press Left or Right on the title screen to show either the black or white highscores. Press Select to show the about screen and build info. In-game press Start to pause and resume. While paused press Select to return to the menu.</p>
-            <p>Collect small white spheres to get +5 white score. Collect small black spheres to get +5 black score. The opposite color will reduce your score when collected. Large black holes will attract you and damage your ship when touched. Large white spheres will repel you and replenish your health when touched. Accelerating will reduce your fuel, which will recharge when not accelerating. You can shoot large spheres for +10 points.<p>
+            <p>Collect small white spheres to get +5 white score. Collect small black spheres to get +5 black score. The opposite color will reduce your score when collected. Shooting while you have a white score will reduce it by one. Large black holes will attract you and damage your ship when touched. Large white spheres will repel you and replenish your health when touched. Accelerating will reduce your fuel, which will recharge when not accelerating. You can shoot large spheres for +10 points.<p>
             <p>For a more detailed description of the original game check out the <a href="https://gta.fandom.com/wiki/Duality">Duality article on GTA Wiki</a>.</p>
         </div>
         <div class="text">

src/game.c

         key_read();
 
         enum ACCELERATION acc = 0;
+        int32_t prev_score = score;
 
         if (key_pressed(J_LEFT)) {
             rot = (rot - 1) & (ROT_INVALID - 1);
 
             if (ret == OBJ_ADDED) {
                 snd_shot();
+
+                if (score > 0) {
+                    score--;
+                }
             }
         }
 
             hiwater = ship_hiwater;
         }
 
-        int32_t prev_score = score;
         int16_t damage = obj_do(&spd_x, &spd_y, &score, &hiwater, 0);
         if (damage > 0) {
             if (debug_flags & DBG_GOD_MODE) {