// Physics simulation functions
function updatePhysics() {
    // Get visible chunks
    const visibleChunks = getVisibleChunks();
    
    // Increment fire update counter
    fireUpdateCounter++;
    
    // Process each visible chunk
    for (const { chunkX, chunkY, isVisible } of visibleChunks) {
        // Skip physics calculations for chunks that are not visible
        if (!isVisible) continue;
        
        const chunk = getOrCreateChunk(chunkX, chunkY);
        
        // Process from bottom to top, right to left for correct gravity simulation
        for (let y = CHUNK_SIZE - 1; y >= 0; y--) {
            // Alternate direction each row for more natural flow
            const startX = y % 2 === 0 ? 0 : CHUNK_SIZE - 1;
            const endX = y % 2 === 0 ? CHUNK_SIZE : -1;
            const step = y % 2 === 0 ? 1 : -1;
            
            for (let x = startX; x !== endX; x += step) {
                const index = y * CHUNK_SIZE + x;
                const type = chunk[index];
                
                if (type === EMPTY || type === STONE || type === WOOD || type === LEAF) continue;
                
                const worldX = chunkX * CHUNK_SIZE + x;
                const worldY = chunkY * CHUNK_SIZE + y;
                
                if (type === SAND) {
                    updateSand(worldX, worldY);
                } else if (type === WATER) {
                    updateWater(worldX, worldY);
                } else if (type === DIRT) {
                    updateDirt(worldX, worldY);
                } else if (type === GRASS) {
                    updateGrass(worldX, worldY);
                } else if (type === SEED) {
                    updateSeed(worldX, worldY);
                } else if (type === GRASS_BLADE) {
                    updateGrassBlade(worldX, worldY);
                } else if (type === FLOWER) {
                    updateFlower(worldX, worldY);
                } else if (type === TREE_SEED) {
                    updateTreeSeed(worldX, worldY);
                } else if (type === FIRE) {
                    updateFire(worldX, worldY);
                } else if (type === LAVA) {
                    updateLava(worldX, worldY);
                }
            }
        }
    }
}