How to reduce lag in projects

I tried making a side scrolling platformer using minimal code and yet it still lags to a point where I can barely play it. Is it just that my computer is slow or Snap in general. Scratch and other things work perfectly its just this version / website that lags my computer. How do I reduce lag if it is "Snaps" fault?

Hi, welcome to the forum!

Did you try it since Wednesday? The new version 6.0 is much faster.

Are you using the touching-color blocks? Detecting sprite-sprite collisions is faster than sprite-color ones.