Experimental expansion of the 54 card version
Base cube suffers from low card count, getting solved after very few drafts and this should give it enough variety to remain interesting with a lot of hidden combos to find.

The cube can be drafted with two players in grid-draft or normal packs with 2 to 4 players. Decks consist of 15 cards with a usual ratio of 10 cards/5 lands. Players start at 1 life and have no mulligans, otherwise normal magic rules apply. I usually play best of 3 matches so both players get to go first at least once.

1. Highly interactive combat with lots of micro decisions and choices for both players in every situation
2. Maximize baseline powerlevel
3. Replayability

Agency is king!
The most fun cards in the cube usually do two or more things at once e.g. have an etb and a keyword or activated ability and give the player multiple use cases and decisions to be made

First turn advantage
There is definitely a lot of pressure on the first and second turn for both players with an obvious advantage for the player going first and playing the offense. This is mitigated a bit by the best of three format which also means that both players have to build their deck to be able to play both roles.

Some cubers have tried to counter this advantage with a free treasure token for the second player or having him start with 2 life. Both feels like crutches to me and doesn't solve the underlying issue.

My approach is to keep most removal on the defensive side and also raising the power baselevel of the cube to allow more explosive responses.

1-Mana removal
should be mostly defensive or low powered/with an upside for the opponent to reduce simple turn two wins with just a 1/1 and removal

Manacost
of single cards should not exceed 3 mana in their base casting mode.
Because the format is very centered around the first 2 turns of each player there can't be too many slots reserved for the very late game/hard control decks as there is no space for rare buildaround cards at 4 mana.

Cards with double mana pips in their cost are also too narrow in my opinion as they may stunt your second turn with two colored decks oftentimes.

Offensive stats
As the games are pretty short compared to normal magic i don't like creatures that stall the game too heavily. That's why i've cut most 0/3 and 0/4 roadblocks even if some of them had some nice effects. They are just not fun to play with or against as they basically just negate one of your opponents creatures without imposing any real threat or advancing the game.

Flying/Menace/Unblockable
Are onesided effects with low interaction and are restricting the cubedesign, bascially creating a second kind of battlefield that only a few cards in the cube can actually interact with. Excluding cards with evasive effects like flying from the cube entirely greatly levels the card balance and simplifies the cubedesign.

Trample
Almost overpowered, because removal on a blocker is basically an auto win

Learn/Lessons
Very interesting mechanic, sadly the cards carrying this keyword are absurdly low powered and the lessons are too expensive and have low impact most of the time. Tested it a bunch and they are just not worth it in the extended version. Great way to expand the 54 card version though.