Yeah, he resigned here. So here's why he resigned. Purple's got 3 moves right now. If he plays j1, he will be flipping the Eastern X-hex to Purple which will give Green the Eastern corner. If he plays the South-East X-hex at f2, he will be giving Green the SE corner. So, Purple's only decent move is to play the South-West X-hex at b6. After Purple plays the SW X-hex at b6, Green can safely play the SE X-hex at f2. This will leave Purple with only one option(remember, our goal is to run our opponents down to ZERO Available Options, AO or OA for short). Purple will then be forced to play their last remaining move at j1, which will give Green the Eastern corner. Purple will now be out of moves entirely. We've accomplished our goal. Green can now simply work FROM the corners... it's GAME OVER for Purple after that. Make sense?
This is mostly achieved by "Running Purple up on the side" and "Finishing with the Sweep" from move #13 and on in this particular game. Every time we do this, we Gain Tempo. Gaining Tempo is HUGE. But it must be done CLEANLY. You can't be flipping outside/exposed pieces when you are "finishing with the sweep." Look through any of my games with Bruno to learn this trick and to see how it's done properly.
If your opponent is the first player to play a side and the piece they are putting on the board is touching one of their own pieces, it ALMOST ALWAYS means they are playing the side incorrectly. There are exceptions, but they are rare. When you see players make this mistake, you can exploit their mistake by "Running them up on the side, and finishing with the Sweep". This will give them an Unbalanced Edge.
If they should choose to NOT take the side, you can take it for yourself. Even though you will end up with an Unbalanced Edge, it's not that bad because you will have what I call an Unbalanced 6, which means all the pieces will be yours, so it can only be exploited from one angle. And you will have gained 2 tempo, so it's worth it because it means you got 2 FREE MOVES while your opponent had to play elsewhere which means they will likely have created new moves for you.