While Action Cards (the cards you hold in your hand and can use on yourself or other players) were not part of the original version of the game, by version 3 I have seen them rise in importance to probably be the most vital element that needs work to perfect the gameplay.
Play testing so far with regards to Action Cards has given a huge amount of insight, and I’m looking at several aspects to refine the way they work.
Some key findings:

1. Action Cards are the primary mechanic to ensure players are not playing solo games
2. Players want to have a variety of cards in their hands at all times
3. Cards should be generic enough to be usable most of the game
4. Players need incentives to use cards and not to hoard them
5. The base probabilities in the game are too low for high impact Action Cards
6. Action Cards need to be simple to explain and remember but interesting and engaging

I’ve had some ideas following on from this, I was thinking about potentially making each Action Card dual purpose – so it can be used on yourself as a buff or an opponent as a nerf – but discussions highlighted this could invalidate point 1 above which I believe is probably one of the biggest weaknesses of the game in its current form.
As a result, my next step for Action Cards is to develop a new set that will consist mostly of small nerfs (negative effects) that should be played on other players at specific times – such as during the selection / matching / post-matching steps of the turn. There will also be additional buffs for yourself, and some form of ‘nope’ will need to be present.
This structure of specific timing during a turn, but hopefully a generic effect that is applicable during most of the game, should encourage players to use their cards when they can as well as pay close attention to what the other players are doing. Hoping to support points 1, 3 and 5.
Small additions to this include a starting hand of 3-4 cards and a maximum number of cards a player can hold in their hands, covering points 2 and 4.
So the final action is to cover point 6 and ensure that the Action Cards themselves have the right level of detail and flavour to spice up the interaction in the game. I guess I’ll get to work!