Suggestions for mind stimulating toys for high energy dogs?

[The Governor]

Hey Everyone!

It's been a little while since I wrote on here but my pup, The Governor, is now a year and a half old and LOVING life!

He is super friendly to everyone he meets (we are still working on the jumping though) and very sociable. He also has the most energy I (or anyone that meets him) have seen in a dog! I take him to dog training once a week, each day he has a 30 min walk followed by 40mins at the dog park (in addition to his other walks during the day that are each 20mins) and I've started looking after a friend's puppy so that he has someone to play with during the day that has as much energy as him! 

I also take him running with me about 5 times a week for 3-5miles at a time yet still he has TONNES of energy. When we are home I try and throw the ball for him and give him himalayan dog chews (they have been a godsend) and we also have a treat ball that he loves.

But I do work from home so need him to be occupied while I am working and wondered if anyone could suggest any great toys/puzzles/games I could try to keep him busy? He is certainly very smart and cottons on quickly so I need something that will keep him busy for longer than 5mins! I don't want to just give him treats and chew things all day, I'd love to keep his mind stimulated too.

Any suggestions welcome!

[Karen, Jasper and Jackdoodle]

Nina Ottosson puzzles: http://www.nina-ottosson.com/products/all-products/

You can get them elsewhere for less, but the website is the best place for seeing the selection. 

[The Governor]

They look great! Thank you!

[Lauren Armstrong]

This probably wont help whilst you are trying to work but for other times train him to find toys and hide them around the house, We did this with our old lab wen he was younger - very how like you describe (labs also take longer to reach adult stage mentality), and we are training our pup now he knows how to find Lucas (my son haha)

We used to hide treats and balls around the house with my old dog and he would sniff them out - obviously we had to get clever after a while but it would keep him stimulated without the need of the toys. 

[Sue harman]

I bought a treat ball and it keeps her busy for a while ! I give her less food and then put her food in the ball , it works very well.