How to prevent a character from climbing mountains?

Question

Game development

A character cannot climb mountains with a simple move, only if he walks and jumps, how to prevent him from jumping out of the mountains? I can make screenshots (If needed)

Answer 1

For example, place an invisible wall above the mountains, or an invisible ceiling at a certain height

Answer 2

Very messy written. What is the final task? Send any traffic in the local network to your DNS?
What, for example, could not use another dns?
Then in Iptables You need to redirect all Udp and tcp requests to port 53
iptables -t nat -I PREROUTING -p tcp --dport 53 -j REDIRECT --to-ports 53
iptables -t nat -I PREROUTING -p udp --dport 53 -j REDIRECT --to-ports 53
All traffic will be redirected to the router.
>Google goes to this DNS adapter, along with DNS from Socks, but you just need it to be from Socks.
Receives via DHCP? then remove Google's DNS output from dnsmasq.