Interesting game. I think there is a collider on top of the cookies that prevents you from jumping on them. I got stuck on top of them a couple times. If you feel like dipping your toes into shaders, there is a really simple combination you can do using Shader Graph to make your portal look much nicer.
Have 5 Nodes in the graph:
* SampleTexture2D - RGBA(4) connects to the shader's Base Color input
* UV > Rotate - Out(2) connects to SampleTexture2D's UV(2) input
* UV > Twirl - Out(2) connects to Rotate's UV(2) input
* Multiply - Out(1) connects to Rotate's Rotation(1) input
* Time - Time(1) connects to Multiply's B(1) input
Have 3 inputs:
* BaseMap - Texture2D - Can be simple texture with straight lines on it. Connect to SampleTexture2D's Texture(T2) input.
* TwirlStrength - Float - Controls how twisted the lines get to make the spinny portal effect. Connect to Twirl's Strength(1) input.
* TwirlSpeed - Float - Controls how fast the portal texture spins. connect to Multiply's A(1) input.
This will twist up the texture you plug into it and spin it around the center making for a neat spinning portal effect.