There aren't though. Dealing with the influx of traffic from a large DDoS attack isn't anything that most hosting providers or servers can even attempt to deal with. After all, how can any server hope to stop someone from sending a large amount of data without processing it somehow?
Dealing with DDoS attacks is precisely why Cloudflare exists, theyre one of the only networks on the planet with the equipment to deal with them properly. See for example the current situation with Belnet, an ISP controlling Belgian Internet services that has recently succumb to a DDoS and come offline. Those things are nasty, especially when you're popular. If an ISP can't beat them, how can an independent gaming website? It's not possible for GBAtemp to have those resources without outsourcing.
I assure you the checks arent as simple as they seem, theres a lot going on behind the scenes, and given it works now its probably correctly learned you as a valid user and won't bother you again until some variable changes.