Hi Skyveon!
Sorry for the performance issues in 0.6.9. The game has received a lot of content updates but needed an optimization patch to make performance more stable on medium to low end machines.
Fortunately we have unloaded all enemies when they are offscreen and reduced their AI calls per second. Plans for future builds is to unload chunks of the stage too, this is way players report better performance on the debug stage as it's much smaller. We'll keep working on the renders until it's lightweight!