Hi! I was following this tutorial on how to set up a Forge mod. The MDK that I downloaded and set up in Intellij compiled fine, so I wanted to try adding an item to the game to make sure it would work. I tried following the code here but my Intellij couldn't find a number of those symbols, like net.minecraft.item.Item, ItemGroup, and net.minecraftforge.fml.RegistryObject. So instead I tried using the code from within the same tutorial here, but I wasn't able to figure out how to import AbstractBlock.
I was thinking this had something to do with the mappings I was using, but I tried using the official Mojang mappings as well as the snapshot ones described in the Forge tutorial, and I was getting this problem regardless. Is there something I'm missing in terms of setup here?