This demo is promising. The progression is fun and doesn’t feel too slow. I think the idea of having upgrades you choose per run is pretty neat. It gives a bit of a roguelike aspect to the game, which makes it more fun to play than the standard “do the same thing over and over again with minor improvements.”
Some suggestions I have, though, are that some of the buildings seem to have a limit on how many you can get. This in itself isn’t terrible since you need to have some game balance, but roguelike games thrive on the fact that you can make stupid, broken builds if you get lucky enough. This game doesn’t have something like that because the buildings you can get are capped at really low levels.
This isn’t a huge problem, but honestly, if you want to make this more fun, I would highly recommend allowing much higher building caps. Perhaps lock upgrading the card caps of some cards behind legacy upgrades. It would make the game much more fun and engaging if you could actually try and go for a broken build and get a large leap in progress because of it. For instance, being able to get a build that has a 5% gold spawn chance and a 20,000% gold value increase with an 80-90% instant respawn chance would be busted and really fun for the player to get due to how much luck is required to get all the right buildings.
I think the game would do well to have more of the legacy upgrades interact more directly with the rogue-like element of the game. Most of the upgrades you get currently are simply passive buffs, which are great, but some legacy upgrades that enhance specific cards, or which change your odds of seeing certain cards, would be nice too.
Overall, this game has a lot of potential to really strike a good balance between the rogue-like and idle genres. I feel like, currently, the rogue-like aspect could be developed a lot more. This, of course, will take heavy rebalancing of the idle side in order to make it so that both idle and active strategies will be viable, but I think with the right upgrades, this game could do it quite well.