I can’t help but feel a little bit responsible for this question, because in a recent review I told you not to invade too aggressively. I tried to show that it would not give you any points and not really take anything from your opponent either.
Of course, it all depends on the tactical particulars of the game.
Many players, myself included, find aggressive invasions annoying. Sometimes I get dismissive; I think my opponent is probably overplaying, doesn’t have a plan, is not reading and merely wants to ‘try something’ to cheat me. I wonder whether, if my opponent was just a bit stronger, they would see that the deep invasion was a bad move and play something more calm instead.
The truth is that players of all levels play like this as a matter of style. It is not (always) overplay. 1kyus like me and presumably dan players still struggle to handle invasions because they are so tactical and diverse. Sometimes the invasion is just the correct move on the board. If it never was, I wouldn’t myself invade, ever.
I’m not strong enough to lecture on the subject and I haven’t looked at your game (I don’t review won games on principle). But because of this feeling of responsibility, and because the thread is still empty, let me share my personal thoughts. This is not commonly accepted Go philosophy and you won’t find these ramblings on Sensei’s Library
So your opponent throws a stone right in the middle of your moyo - what should you do? You can prepare yourself by doing tsumego until your hair catches fire, then read out all the variations and pick the best one.
Let’s scrap that approach right away. Calculation is for computers. We need a way of thinking that uses human qualities like common sense reasoning, and the view that you get when you look at the board through human eyes, not a bunch of numbers (if that makes sense).
What you should do first is remind yourself that Go is a balanced game of sharing. No player can get less than half of the board unless they make a mistake. A player who loses by 10 points has made 10 points worth of mistakes (if their opponent is perfect).
While you keep this in mind, ask yourself how much you deserve. If your moyo (in very vague terms) has a potential of 50 points and can be reduced to 30 points, you deserve to get 30 points.
Let’s say your opponent does the invasion. You skillfully capture and kill it. Now your moyo is 50 points of solid territory (influence balance is magically accounted for in this). Your opponent has made a blunder of 20 points!
Let’s say that the best move on the board is also worth 20 points (it might be, in the middle game). Your opponent’s blunder is the same as a pass!
Is this realistic? The invasion may be dubious - call it bad style or whatever. But as long as it is a purposeful move, it must be better than a pass. You should not start from the assumption that your opponent makes moves without purpose.
So it is theoretically impossible, if Go is truly balanced, for you to get these 50 points. There must be some benefit for the invader. If you cannot see what it is, it will still be on the board, but in hidden form (aji, counterattacks etc). Sooner or later this benefit will manifest itself and catch you by surprise.
My approach (in an ideal world, not actual games ) is to assume that my opponent has not blundered so severely. Instead, I come to terms with the fact that the invasion will live or escape. The moyo is split.
Start looking for things you would like to keep (e.g. the bigger of the 2 parts) and strengthen that.
Figure out where the compensation is. It is impossible for the deserved points to disappear - either they were never there, or they have gone somewhere else. Erased points can transform into influence, counter-attacks or simply points in other places (tenuki/miai).
If you follow proverbs diligently (drive opponent towards thickness; enclose before reduce before kill; don’t play in front of thickness etc), you are more likely to uncover the compensation in the position. Otherwise, the compensation will stay unused and fade away, for example if you attack from the wrong direction.
Part of compensation is that you get to attack the invader severely, so don’t take all this as a suggestion to play passively. That is not the same thing.
I believe that the best path to avoid complication and therefore, minimize risk, is to take not more than you deserve. What you don’t deserve, you must allow - and even encourage - your opponent to take.
Finding out what it is that each player deserves can be tough. You need accurate, impartial positional judgement, emotional detachment and a cool head.
As a rule of thumb, you can play according to your need. Need 20 points to win? You deserve them, so surely they must be somewhere. Go get them, whatever it takes!