Elemental reactions, like shooting a dynamite-filled barrel or using an ice spell to cross a stream, are an important way for designers to bring worlds to life.

Too often game worlds can feel like static backdrops for gameplay. But by incorporating elemental reactions, developers bring complexity and characterization to a players surroundings.
By now were all familiar with the overused exploding barrel trope. A single bullet is all it takes to create an explosion that can take out multiple enemies, turning an element in the environment into an interactive arrow in your quiver as you progress. While environmental storytelling has stolen the spotlight when it comes to designing spaces, emergent environmental narrative design is quietly the bigger innovation happening in games right now, with elemental reactions being the easiest to grasp.
If games are big iterations of cause and effect, then elemental reactions give very clear and logical feedback to players about exactly what their footprint on the world is. Whats more, modern games that embrace elemental reactions, like Divinity: Original Sin, Genshin Impact, and Noita, also give their worlds and characters more personality and texture, creating a space thats much more alive and free-flowing than you normally see in game worlds.
The exploding barrel example works like this: You wait until enemies are in proximity of the barrel, then you ignite it somehow, causing it to combust and send them flying. Cause and effect here are clear, and the game world becomes part of your strategy. Suddenly the environment becomes more of a third party that you can use and interact with. In the old days of games like DOOM (1993), this meant keeping an eye out for more exploding barrels, but games eventually got better at environmental interaction by looking to other elements.
One classic example is water puddles used in tandem with electricity powers in BioShock (2007). Just like the exploding barrel trick, you have to wait until enemies are in position, but here the impact area is marked by the wet floor, so you can clearly see who and what will be affected. More importantly, though, is the fact that this interaction is immediately apparent without much explanation to the player. Of course zapping a water puddle will electrify anyone standing in it. Basic elemental reactions are effects that everyone can intuit.
At the same time, elemental strengths and weaknesses, both explicit and implicit, have been part of role-playing games and card games since the beginning, with roots stretching all the way back to tabletop RPG Dungeons & Dragons (1974) and reaching an apotheosis with Pokémon, in both video game and trading card game form. The backbone of both Pokémon games is a complex chart of type strengths and weaknesses, making for a convoluted game of rock, paper, scissors. Its why elemental diversity is generally encouraged in most competitive Pokémon teams, and though card decks cant be diverse by design, they can work to mitigate any disadvantages they come across. Every Pokémon type becomes something of a character in and of itself.
Of course, Pokémon generally doesnt deal with interesting combination effects very often, merely doing more or less damage. Recent smash hit Genshin Impact takes this a step further and weaves elemental reactions into both combat and exploration. You play as a party of characters that you can swap among on the fly, each of which has an elemental quality to their powers. Combining certain elements will create new effects that can make your strikes more powerful, impede the enemy, or even get you more resources. Combining ice and electricity, for example, makes the superconduct effect, which deals ice damage in an area and reduces physical resistance. And the fact that you can switch between characters on the fly means that you can smoothly create some big effects, depending on what youre facing, in the blink of an eye.