Added proper taggins for gravity

internal/maps/plains.go

@@ -13,13 +13,48 @@ func CreatePlains(screenWidth, screenHeight float64) *Map {
 	m.BackgroundColor = color.NRGBA{R: 135, G: 206, B: 235, A: 255}
 
 	// ground surface
+	groundColor := color.NRGBA{R: 34, G: 139, B: 34, A: 255}
 	m.World.AddSurface(&world.Surface{
 		X:      0,
 		Y:      screenHeight - config.GroundHeight,
 		Width:  screenWidth,
 		Height: config.GroundHeight,
 		Tag:    world.TagGround,
-		Color:  color.NRGBA{R: 34, G: 139, B: 34, A: 255},
+		Color:  groundColor,
+	})
+
+	// Platforms
+	// Use ground color by default as requested
+	platformColor := groundColor
+
+	// Platform 1: Low left
+	m.World.AddSurface(&world.Surface{
+		X:      100,
+		Y:      screenHeight - 120,
+		Width:  150,
+		Height: 20,
+		Tag:    world.TagPlatform,
+		Color:  platformColor,
+	})
+
+	// Platform 2: Mid center
+	m.World.AddSurface(&world.Surface{
+		X:      350,
+		Y:      screenHeight - 200,
+		Width:  200,
+		Height: 20,
+		Tag:    world.TagPlatform,
+		Color:  platformColor,
+	})
+
+	// Platform 3: High right
+	m.World.AddSurface(&world.Surface{
+		X:      650,
+		Y:      screenHeight - 280,
+		Width:  150,
+		Height: 20,
+		Tag:    world.TagPlatform,
+		Color:  platformColor,
 	})
 
 	// left portal to desert