How we designed Burger Stack, a cozy burger stacking puzzle

Burger Stack is a 3D burger stacking puzzle for iPhone. Every level starts with a row of plates holding mixed-up piles of buns, patties, cheese and vegetables, and an order ticket pinned above the counter. Your job is to rebuild those piles into the burgers on the ticket.

The whole game rests on one rule we never break: you can only move the ingredient on top of a plate. Tap it, then tap another plate, or simply drag it across. Anything buried underneath has to wait until the pieces above it have been moved somewhere else. That single limit is what turns a tidy-up into a real sorting puzzle, because every move changes what you can reach next.

Plates also have a height limit. A plate can hold as many ingredients as the tallest burger in the level, and each plate shows how full it is with a small counter. Try to add one more and the game tells you the plate is full instead of letting the stack topple. When a plate holds a finished burger from the ticket, its counter switches to READY.

Every level gives you two empty plates on top of the ones you need for the order. We think of them as the cutting board of the kitchen: a place to park a slice of cheese or a top bun while you dig out the patty you actually need. Learning to use those two buffers well is most of the skill in Burger Stack, and the How to play card says it plainly: empty plates give you room to work.

The order ticket is the only instruction a level needs. It shows the recipe as a row of ingredients labelled bottom to top, plus how many of that burger the kitchen wants. You always build upwards, starting with the bottom bun and finishing with the top bun, exactly as a real burger is assembled.

Because order matters, a correct pile of ingredients is not enough. A Classic burger is bottom bun, lettuce, patty, cheddar and top bun, in that order. A patty sitting under the lettuce is a mistake you have to undo by moving pieces off and back on. That is where the planning comes from: you are not just collecting the right food, you are sequencing it.

Some recipes repeat an ingredient on purpose. The Double cheese burger stacks patty, cheddar, patty, cheddar, and the Garden burger uses lettuce twice. Identical pieces are interchangeable, which gives you more freedom, but it also means you have to keep count. Later recipes switch from the classic bun to a pretzel bun, so a bottom bun from one burger will not work as the base of another.

From level 25 the ticket can list two different recipes at once. We call these mixed orders: the ticket shows a separate line and a separate count for each burger, for example two Veggie and two Classic. Mixed orders are where the bottom-up rule really bites, because two recipes compete for the same plates and sometimes for the same ingredients.

Burger Stack has 72 levels split into 9 chapters of 8 levels: Classic, Tomato and Onion, Breakfast, BBQ, Crispy Chicken, Swiss, Steakhouse, Golden and Master Chef. The levels sit on a winding map. After the opening chapter the recipe changes every 4 levels, so there is always something new on the ticket without overwhelming you.

We ramp difficulty with a few dials and we try never to turn them all at once. The first is the number of burgers in the order: 2 in the first five levels, 3 up to level 15, then 4. More burgers means more plates and more ingredients to keep track of. The second is how tall the recipes are, from five ingredients to six. The third is how thoroughly the plates are shuffled at the start, which also sets the par shown next to the move counter.

Level 25 is a good example of the dials working against each other. It is the first mixed order, so we drop it back to 3 burgers and use a much lighter shuffle than the level before it. The new idea gets your full attention, then the pressure builds again over the following levels. The same thinking applies to new recipes: when a brand new burger debuts inside a mixed order, it is always paired with a recipe you have already made.

Every level is built backwards. We start from finished burgers and two empty plates, then shuffle them with legal moves only, following the same top-ingredient and height rules you play with. That means every one of the 72 levels has a solution, and our rule tests replay that solution on every single level. The shuffles are fixed, so every player gets the same level 40 and can compare runs.

We wanted Burger Stack to be a cozy puzzle you can play on the sofa or on a train, so there is no timer anywhere in the game. You can look at a level for as long as you like before making the first move. If you leave mid-level, the plates are saved and waiting for you when you come back.

Undo is always on screen. Each level gives you five free undos, and the button shows how many are left. Restart sits right next to it and puts the level back to its starting shuffle, while keeping any stars you have already earned on it. We wanted mistakes to feel cheap, because in a sorting puzzle you often only see the right plan after trying the wrong one.

There is one small catch, and it is deliberate: an undo still counts on the move counter. Taking a move back gets you out of trouble, but it does not erase it from your score. That keeps undo friendly for learning while making a clean solve feel like a real achievement.

For players who get stuck, two optional boosters can help. Extra plate adds one more empty plate for the rest of the level, and Secret sauce finishes one burger for you without touching the ones you already completed. Both are there to keep the game moving, never required to beat a level.

Each level shows a par, a move target we set from how the level was shuffled. Finish at or under par and you earn three stars. Stay within twice the par for two stars. Any finish earns at least one star, so you can always move on to the next level. Par is generous by design: three stars should feel within reach once you have spotted the plan.

Only your best result on each level counts. Replaying a level can raise its stars, but it never pays the same stars twice, so the total on the map always reflects how well you have played, up to 216 stars across the 72 levels.

Stars are what open up the restaurant. At 6 stars you add ingredient crates, at 18 kitchen plants and at 42 a service window, and each upgrade appears in the 3D kitchen behind the plates. At 12 stars you unlock the Coastal diner and at 36 the Evening bistro.

Finishing a level for the first time also pays coins: 20 for the clear plus 10 for every star. Replays pay a smaller bonus plus coins for any new stars, and every win adds a few coins to a tip jar you can empty later. A daily calendar adds a small gift for each day you drop by.

The menu has 14 burgers built from 18 ingredients: bottom and top buns, pretzel buns, patty, veggie patty, crispy chicken, steak, cheddar, Swiss cheese, lettuce, tomato, ham, onion rings, fried egg, bacon, pickles and ketchup. Ingredients have their own landing sounds, from the crunch of lettuce to the soft thud of a patty, so you can almost hear a burger coming together.

The recipes are Classic, Tomato, Double cheese, Onion ring, Breakfast, Veggie, Bacon BBQ, Ham melt, Crispy chicken, Garden, Swiss deluxe, Steakhouse, Pickle party and Golden tower. The Golden tower is the last one to arrive, at level 57, and stacks a pretzel bun, crispy chicken, bacon, fried egg and Swiss cheese under the pretzel top.

The recipe book collects them all. Unlocked burgers show their ingredients in order with a bottom to top reminder and a View 3D button to turn the finished burger around. Locked burgers show which level unlocks them, so the book doubles as a preview of what is coming. When a level adds a new recipe, the win screen tells you it has gone into the book.

The kitchens change the mood, not the rules. There are 6 of them: Corner kitchen, Coastal diner, Evening bistro, Candy parlor, Neon night and Golden grill. Each has its own floor, lighting, furniture and props, from the warm lamps of the bistro to the pink and blue neon of Neon night. The first three are earned with stars, the other three are found in the shop, and your chosen kitchen stays with you from level to level.