Add hero banner to README

as6/README.md

@@ -7,6 +7,8 @@
 Steer a probe in space by placing black holes, collect stars, and survive a
 continuous stream of hazards.
 
+![Hero banner of gameplay](docs/hero.png)
+
 [Play the web version!](https://gravitysurfing.sandvich.xyz)
 
 </div>
@@ -30,8 +32,8 @@ continuous stream of hazards.
 
 - You control a probe that moves continuously through a side-scrolling world
 - Black holes/gravity wells bend the probe trajectory with inverse-square pull
-- Gravity meter limits how often you can steer aggressively
-- Stars restore meter and increase run score
+- Consume energy meter to place black holes
+- Stars restore your energy meter and increase run score
 - Asteroids and out-of-bounds movement end the run
 - Null zones disable gravity influence and force repositioning
 
@@ -40,7 +42,7 @@ continuous stream of hazards.
 - `enter` - start run (menu), retry run (death screen)
 - `Esc` - Close game
 - `m` - toggle mute
-- `left click` - place/use player gravity black hole (if you have enough meter)
+- `left click` - place/use player gravity black hole (if you have enough energy)
 - `right click` - clear active player-created black holes
 
 ## 🛠️ Technology Stack
@@ -106,9 +108,9 @@ continuous stream of hazards.
 
 3. **Play and survive**
 
-   - Left click to place/use gravity black holes when meter allows
+   - Left click to place/use gravity black holes when energy meter allows
    - Right click to clear player-created black holes
-   - Collect stars to refill meter and increase score
+   - Collect stars to refill energy meter and increase score
    - Avoid asteroids and avoid leaving the screen bounds
 
 ### 🌐 Web/WASM Build
@@ -156,7 +158,7 @@ continuous stream of hazards.
   tactical placement
 - **Procedural spawning**: stars, hazards, and null zones spawn based on scroll
   position
-- **Event-driven feedback**: collectible, meter, and death callbacks keep
+- **Event-driven feedback**: collectible, stats, and death callbacks keep
   systems loosely coupled
 
 ## 🗂️ Project Structure