Happy I could help.
I was using a mid-range laptop when I played but that seems like a weird reason for the graphics thing you mentioned. I don't build to web player so not familiar with the setup.
What do you mean "it depends on the pc's GPU". afaik Unity doesn't have some kind of option to set the graphics based on the machine spec and it's left to the developer (or it defaults to the "default" graphics level in the preference settings). is the web player different?
are you specifically changing it yourself? if so, not sure why. using the same machine as the "lowest" spec for the game I am making and it runs perfectly fine (I don't want to hijack your thread and post screenshots but checkout my profile if you want to see what I'm talking about).
Either way, good luck with your game.
Viewing post in NIGHT INVASION
Here's a few tips since you're using Unity.
1) Use Linear color space and not Gamma.
Edit > Project Settings > Player > set "Color Space" to "Linear" (it's Gamma by default)
https://docs.unity3d.com/Manual/LinearRendering-LinearOrGammaWorkflow.html
2) Use deferred rendering when possible for scene cameras.
Select the Camera > Rendering Path > Deferred
https://docs.unity3d.com/Manual/RenderTech-DeferredShading.html
3) Checkout occlusion culling if you don't know what it is
https://docs.unity3d.com/Manual/OcclusionCulling.html
4) Batch draw calls
https://docs.unity3d.com/Manual/DrawCallBatching.html
5) General optimisation tips for graphics
https://docs.unity3d.com/Manual/OptimizingGraphicsPerformance.html