Stack the Deck is a format where players build a 60-card deck but before each match, they stack it: they choose the order of every card in the deck. They then play games as normal.
Deck building rules are as usual except for one exception: no card, attack, ability or effect can shuffle either of the decks. Essentially, it means there’s no search or hand disruption: the state of the deck must always remain as stacked in the beginning. You can play a card that puts a single card either to the top of the deck (like Academy of Night) or bottom of the deck or play cards that specifically tells player to reorder X cards (like a single copy of Puzzle of Time) but nothing that randomises the deck.
The game then becomes a puzzle at the deckbuilding time: how do you maximize the odds of winning the game when you know everything that’s gonna happen with your deck.