The game featured a store and stuff in it, that's a product category IKEA markets.
If the name of an unrelated game was IKEA as some clever acronym or such and it was unrelated to stores, that would be a different trademark convo.
If the name of an unrelated game was IKEA as some clever acronym or such and it was unrelated to stores, that would be a different trademark convo.
Ultimately, these matters would likely be decided in court. IANAL either but it seems like the game maker would have a strong case. Among the things IKEA would have to prove is actual harm and confusion, who would seriously argue that? That doesn't mean IKEA couldn't make it impossible to fight with their unlimited legal resources, I can understand not wanting to spend a chunk of your life on that.
Two things can be true at once: this is the most creative marketing in recent memory and genuinely funny, and IKEA destroyed someone's work simply because they can.