I wanted to add Monster Hunter's equipment crafting and upgrading to this project somehow. While I could take a more RPG-ish approach, and add monster drops and whatever for the required materials, I decided to use cards as materials instead.
There was a choice between requiring specific materials or requiring a certain combined value. If I was going to require specific materials, I could either choose each required material by hand for each upgrade (Monster Hunter's approach), or I could just write some kind of hash function to create the required materials.
The problem is, the player has little control over what materials are obtained. The player can choose which booster pack to purchase, but that's pretty much it. So instead, I chose the other approach, as shown in the video.
Players can choose up to five cards each upgrade. Cards of higher rarity provide more points towards an upgrade. These points don't carry over in any way, so players can't just dump a bunch of low-rank cards to reach the max level.
Also, adding points above the required amount won't affect the new stats, or count towards future upgrades.
The title screen theme is an arrangement of the song used here. Because every RPG needs a playable piano, I think I'll be using this song for that purpose.