From the slow advance of Tetris to the considered placement of fruit in Suika game, games about dropping things are an eternal fixture of games. So let's have a look at what makes these games tick.

The core loop:

Key elements:

Starting with the player dropping the object, a decision that can be as simple as choosing x-axis position, the player then gets to view a domino-like progression: Have they dropped in the right place? How much do they score? How much are they going to regret dropping it there?

This sequence helps give each drop just a hint of tension, coupled with the beginning of planning the next move.

Failure state: the top of the screen is reached

The share failure state across games in the genre is reaching the top of the screen. This shared condition helps with onboarding new players, demonstrated nicely by Suika-game going viral on the english speaking web before its official translation, any player or viewer immediately understood how not to lose. But with the continual placement of objects into the play space, we have a problem: How does the player not just inevitably lose? This leads directly into the second core mechanic, clearing space.

Clear space:

By removing rows or making bigger fruit, the player gets to stave off the end. In Tetris this is a strict benefit, clear the row, get yourself some breathing room (We’ll come back to the risk reward later). In Suika game this is a Faustian bargain, as while combining two fruits into a bigger one does give you more space, the bigger fruit are also more difficult to place subsequent fruit around as they trap smaller fruit beneath them.

Why does it work?

Small decision space

Each time the player drops an object they have a very limited range of positions to drop it from, and the correct decision is based only on what they’re dropping and what they’ve dropped already. This lets players avoid option paralysis and over-analysing their next move, helping with new player onboarding. 

While games like Tetris add additional factors to this decision like rotation, the options are similarly limited and are often segmented from the dropping position decision. The play space being initially empty also helps here, as players have a few turns of safety to learn the controls before things really get going.

The limited decision space also lets players build to long term planning, making sequences of small decisions with reasonably predictable results, with the sprinkle of randomness from upcoming objects becoming more of a factor as players get better..

Consequences of my actions

Another pillar of the genre is that players build their own challenges. Every annoying block or fruit trapped is a direct result of a player's previous actions and mistakes. This helps create a sense of fairness and makes player improvement obvious, as a player getting better both lets them avoid obstacles and avoid creating obstacles, resulting in longer play sessions and higher scores. 

Theme flexibility: Juice it up or Calm it down

The simple and abstract nature of the core mechanics allows for a lot of room for theming. There are broadly two directions to go in this regard: Cozy and Meditative or Juicy. These are nicely shown off by Suika game and Cosmic Collapse, which feel like very different games despite their similar mechanics.

Design Considerations: 

The great divide: Realtime vs Turnbased

One thing which separates Tetris and Suika game, and acts a dividing rift in the genre, is whether or not the player is under time pressure to decide where they’re dropping something. This decision has many knock on effects: realtime adds reflex challenges, which can potentially increase over time for a difficulty curve, and puts pressure on forward planning.

Time pressure can also lead to death spirals, as players make mistakes they reduce the playspace, giving themselves less time to act next time round, causing them to make more mistakes. This isn’t strictly a negative. It can help to end games where a player has already lost quickly, reducing frustration. It can also produce exhilarating moments of snap recovery from the brink, followed by a pressure release as the game gets easier with the increased playspace.    

Adding the friction

While we've looked a lot at how gentle fairness is important, there is also a need to throw a wrench in players' plans. S and Z Tetromino exemplify this, a tetromino with no safe arrangement, guaranteeing an unfilled slot unless the board has been prepared for their arrival. In Suika game this comes from getting fruit which don’t match ones which are already accessible on the board, and the slightly unpredictable ways the circular shapes of the fruit roll and trap each other.

SandTrix demonstrates just how much friction you can add, with trying to connect the piles of sand feeling like herding cats. This level of friction probably only works as subversion and because the audience is familiar with Tetris, the feeling of having the rug pulled out from under you as the blocks crumble to sand.  

Ramping up or permanent mistakes

Usually you don’t want players to be able to play forever, if for no other reason than they’ll probably hit an integer overflow at some point. So the question is: How do you create a growing resistance?

In real time games you can do this by upping the speed objects drop at, forcing mistakes and nonoptimal placements. Getting this right can be tricky, as you’ll probably be much better than your players, so playtesting this approach is key. Ramping too fast won’t give a chance to learn but ramping too slow will make the game dull on replays, as players wait for the game to match their skill.

For turn based examples this returns to the consequences of the players actions we discussed earlier, by making it difficult or impossible to recover from certain mistakes. This results in a player being slowly crushed by their previous placements and errors. You do need to be able to force these errors however, such as by varying what the player drops. 

Accessibility

The simple control schemes (often only 3 buttons) and confined playspace create a good starting point for making the games accessible for disabled players. Two key elements to build on are:

One button control schemes. 

For example Tetris’s 3 buttons can be mapped to 1 using the following scheme:

• One press move the piece left
• Double press moves the piece right
• Hold rotates the piece

(This is far from the only mapping, and slightly more complex alternatives which hold the piece at the top of the screen to allow horizontal positioning first would probably be better in practice)  

Second channel description of the playspace. This provides access for blind players and players with low vision, additionally if the game relies on colour to convey information (for example Sandtrix) then this removes a barrier for colour blind players. This could be a promptable audio description of the position of objects, a cursor which lets players explore and ping different locations to find out what's there, or additional symbols on objects to supplement colour information. Real time games in the genre do present more design challenges for accessibility. This is because second channel approaches are often slower at conveying information than visuals.   Appropriate options to affect game speed to let a player adjust for this, as would the ability to pause as the game describes the current state of the playspace.

C-c-combos!

To add a small layer of spice to play you can employ risk-reward mechanics as players push for highscores. Tetris’s eponymous 5 line clear bonus is an example of this, as is Cosmic Collapse’s combo multipliers for multi-combinations made in single drops. Combos can be done in two ways: The initial placement reward of Tetris, or the domino clears of Suika game. 

This is one of the things which separates Tetris and Sandtrix, placing a block will never result in knock-on clears in Tetris, but can result in them in Sandtrix.

Circling the Square: Atomas

Atomas is a science themed game which turns our row clearing genre into a circle clearing one. Players place atoms in a circle, lose when the circle is filled, and clear space by using “Plus Atoms” to merge adjacent atoms into heavier ones. The shared failure conditions and space clearing mechanics, as well as the simple decision space, fit it nicely into the genre.

Atomas demonstrates an interesting potential mechanic: the manual merge. This is where the player chooses when space clearing happens, rather than it being automatic. In Atomas this is used to let the player setup large combos, daring them to pile more atoms onto the field before clearing them, hoping they get a Plus atom in time.

Neighbours: Triple Town

Just as Atomas twists the genre’s shape, Triple Town shifts its perspective, moving to a grid rather than a box. This shift changes the failure condition: Having the playspace be filled completely, but preserves the space clearing: sets of 3 adjacent buildings are merged into a higher level building.

An element Triple Town brings in is that of turn sequencing. Bears move around the map, blocking spaces and needing to be corralled. This helps to make dropping sequences of elements interesting, as sometimes you should place in a suboptimal position to block bears or delay merging to keep them contained. It also provides a ramping challenge as more Bears become present through a level and proportionally occupy more of the playspace as it fills. 

Ludography:

Tetris by Alexey Pajitnov

Sandtrix by mslivo

Suika Game by Aladdin X

Cosmic Collapse by Johan Peitz 

Atomas by Sirnic Games

Triple Town by Spry Fox