Excellent deck-building roguelike Slay the Spire has now sold one million copies, developer Mega Crit Games said this week as it unveiled a new game mode that allows you to craft custom dungeon runs.

Custom mode, Slay the Spire's third game mode, offers a variety of modifiers to switch on and off that will drastically change your next run. You can jump into the custom dungeon yourself, or share your options with others for them to try.

The 15 or so modifiers can both make the runs easier or harder. For example, one will let you pick your own custom deck before the run starts, while another changes the map so it only contains one path, cutting down your options. Some will add specific cards to your deck to alter your play style. Switch on all the difficult ones and you'll create a near-impossible challenge.

To unlock the mode, you'll first have to complete one of the difficult daily challenges, which will earn you the "My Lucky Day" achievement.

"Our aim is to expand this mode to allow new challenges such as Endless mode (which is still being worked on in Beta) and eventually allow players to create, incorporate, and access mods through this flexible interface," the developer said in a Steam post. See a quick gif of that interface below.