hard drop shake effect added

src/graphics/renderers/GameRenderer.cpp

@@ -1983,6 +1983,39 @@ void GameRenderer::renderCoopPlayingState(
     }
     SDL_SetRenderDrawBlendMode(renderer, SDL_BLENDMODE_NONE);
 
+    // Hard-drop impact shake (match classic feel)
+    float impactStrength = 0.0f;
+    float impactEased = 0.0f;
+    std::array<uint8_t, CoopGame::COLS * CoopGame::ROWS> impactMask{};
+    std::array<float, CoopGame::COLS * CoopGame::ROWS> impactWeight{};
+    if (game->hasHardDropShake()) {
+        impactStrength = static_cast<float>(game->hardDropShakeStrength());
+        impactStrength = std::clamp(impactStrength, 0.0f, 1.0f);
+        impactEased = impactStrength * impactStrength;
+        const auto& impactCells = game->getHardDropCells();
+        const auto& boardRef = game->boardRef();
+        for (const auto& cell : impactCells) {
+            if (cell.x < 0 || cell.x >= CoopGame::COLS || cell.y < 0 || cell.y >= CoopGame::ROWS) {
+                continue;
+            }
+            int idx = cell.y * CoopGame::COLS + cell.x;
+            impactMask[idx] = 1;
+            impactWeight[idx] = 1.0f;
+
+            int depth = 0;
+            for (int ny = cell.y + 1; ny < CoopGame::ROWS && depth < 4; ++ny) {
+                if (!boardRef[ny * CoopGame::COLS + cell.x].occupied) {
+                    break;
+                }
+                ++depth;
+                int nidx = ny * CoopGame::COLS + cell.x;
+                impactMask[nidx] = 1;
+                float weight = std::max(0.15f, 1.0f - depth * 0.35f);
+                impactWeight[nidx] = std::max(impactWeight[nidx], weight);
+            }
+        }
+    }
+
     // Draw settled blocks
     const auto& board = game->boardRef();
     for (int y = 0; y < CoopGame::ROWS; ++y) {
@@ -1992,6 +2025,18 @@ void GameRenderer::renderCoopPlayingState(
             if (!cell.occupied || cell.value <= 0) continue;
             float px = gridX + x * finalBlockSize;
             float py = gridY + y * finalBlockSize + dropOffset;
+
+            const int cellIdx = y * CoopGame::COLS + x;
+            float weight = impactWeight[cellIdx];
+            if (impactStrength > 0.0f && weight > 0.0f && impactMask[cellIdx]) {
+                float cellSeed = static_cast<float>((x * 37 + y * 61) % 113);
+                float t = static_cast<float>(nowTicks % 10000) * 0.018f + cellSeed;
+                float amplitude = 6.0f * impactEased * weight;
+                float freq = 2.0f + weight * 1.3f;
+                px += amplitude * std::sin(t * freq);
+                py += amplitude * 0.75f * std::cos(t * (freq + 1.1f));
+            }
+
             drawBlockTexturePublic(renderer, blocksTex, px, py, finalBlockSize, cell.value - 1);
         }
     }