I just gave the game a try and it is a lot of fun!
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Thanks for the fun hour or so I played for! 
Glad you liked it.
I've made this game primarily for my father. He use to play this a lot in real life with a number of people, including his parents, many of them dead for more than 40 years by now.
I did a much simpler version of this maybe 15 years ago when I learned to "program" to help my youngest son who wanted to make computer games.
When I learned this summer that my father still is playing that old game and enjoying it, I decided to make a newer better version of it. So I prolonged the break from doing the Jacqueline White game with a couple of days to do that.
Well done on the computer A.I. for Adam, Bertil, and Carl. Do they have different levels of skill or do they all run the same way? I'm just curious because Bertil seemed the best, then Adam, then Carl, but it's probably just coincidence.
There is a function to mimic the effect of draw cards to improve the hand for the AI-players. This might possibly favor one artificial player over another.
In 5-cards the same functions are used for all of the AI-players.
I read the rules before playing and the poker rules were pretty clear, but the 5-card rules I couldn't figure out after three readings. It says "trick" sometimes and then "stick". It says "colour" instead of "suit", making me think that any red card was fine if the first card was hearts, for example.
"Stick" is the word use in Swedish for one round of cards (one card from each player). "Trick" is the word I thought would say the same thing in English. "Färg" (=color) is in Swedish the word used in card games for suits. The 5-card rules was a bit tricky to describe in a few words. I'm quite uncertain on much of the vocabulary for this in English.
I'm sure there a possibilities to improve the English texts.
After figuring out the rules on my own there was one thing I still could not understand: Sometimes I'm forced to play a higher card and sometimes I'm not. I couldn't figure out why the game was doing that sometimes but not other times.
As a player one must play a card in the suit of the highest card of the trick if you have one and you must beat the highest card played in that trick within that suit if you can. You may not save the higher card to use it later. If you have more than one card that can beat the high card you may play the lower one of those two. As long as you beat the high card it is OK. The first card of the trick decides the suit. A card in the suit played later in the trick can become the highest. If you don't have a higher card (in the suit) you play a lower one and if you don't have a card in the suit at all, you can play any card you have (preferably one you don't think will be useful later on).
That is what the system should enforce. I thought I had that working as it should. If it doesn't then there is a bug.
Since I have not seen the actual trick it is hard to have an opinion on if it was wrong and, if so, what went wrong.
A very slight thing also but: I found sometimes the suits and numbers/letters to be a bit hard to see on the small cards. It was easy to get used to, but I did make a few mistakes in 5-card at first because of this.
It can be a bit hard, I agree. That is why I added color to the cards to make it easier to see which suit it is.
One way could be to make the small cards bigger, but I didn't think that gave the same feeling. So it is a bit of a trade of.
You also have the information of which is the high card in text (top left).
It works for my father and he doesn't see very well any more.
I also think I found a glitch. Nothing game-breaking but: If you pop some cards up after the poker hand is over, they remain popped up during the 5-card round, and also remain popped up after the next poker round starts. There's no reason to pop the cards after the poker hand is over, so why not just disable the function?
It is supposed to be disabled during the 5-card, but apparently there is a window of opportunity to "pop" the cards before that starts working. Should not be hard to fix.
It would be a great minigame in a longer game too, although I suspect that might already be in your mind.
Could well happen. Perhaps not exactly this game but something like it.