Nature and effects
Learning paths through this topic
Make smoke, fire and magic particles fade in softly and change colour as they age
Particles that pop into existence at full strength and vanish at the end look cheap, and fire that keeps one colour looks like a sticker. Describe how each looks over its whole life with a few numbers. Here is the age-to-look rule, including the trap of blending additive glows.
Show a plant that grew while you were away stage by stage, not in one jump
When a player comes back to a garden after a day, a plant that jumps from seedling straight to full size feels like nothing happened, and a slow replay of every stage wastes their time. Here is how to play only the stages that were passed, in order, at a speed that never takes longer than a moment.
Simulate a lively water surface that settles down and never explodes
A row of water columns that react to drops and splashes looks great until a low frame rate or a strong splash makes the whole surface shoot to the sky. And a surface that slowly loses or gains water gives the wrong level in the end. Here is a stable step with a clear limit, and a way to keep the total volume.
Make a bog or quicksand pull down harder the more the player struggles
A bog that kills you in a fixed time is just a timer, and one that does not react to your input is unfair. The fear in such a scene comes from the rule that moving fast is what sinks you. Here is the rule, how to keep it readable, and what makes holding still a real way out and not a loophole.
Slant rain streaks by wind and by how the camera moves past them
Rain that falls straight down on a side-scrolling street while the character runs looks glued to the screen, and rain that ignores a gale looks calm. The slant, the length and the speed of each streak come from the same few numbers. Here is how to get them right, with near and far drops moving differently.
Let rain stop at a roof or an umbrella and splash on whatever it hits
Rain drawn as falling lines across the whole screen looks wrong in a scene with a porch, a bridge or a character with an umbrella: the drops pass straight through. Checking every drop against every roof is costly on a phone. Here is a rule that needs no list of drops and still ends each line at the right height.
Place a rainbow in the sky from the sun's height, and know when it cannot show
After the storm in a story, a rainbow is the sign that it is over, but a bow painted at a fixed spot looks wrong the moment the player turns or the sun is high. Real bows have a fixed size, sit opposite the sun and cannot appear at noon. Here is how to place one correctly, including the faint second bow.
Make raindrops crawl down a window in jerks and merge when they meet
A rainy window is the classic quiet scene in a story game, and drops that slide down at a constant speed look like falling beads on a string. Real drops cling, then rush, then cling again, and big ones eat small ones. Here is how to get that behaviour with predictable results.
Scroll a river in lanes at different speeds without seams or shimmer
A scrolling water picture is the cheapest river there is, but it often shows a gap that flashes at the join, scrolls the wrong way for a downstream current, or shimmers when pixel art moves by fractions. Here is how to place the copies so the water always fills the view and sits still on the pixel grid.
Pick today's weather so everyone sees the same and no streak runs on forever
A daily weather in a casual game is a nice shared moment, but throwing a die each day gives long sunny stretches or three storms in a row, and different phones in different time zones disagree. Here is a way to make the weather depend only on the date, keep the mix you want, and keep streaks short.
Fade between two outdoor backgrounds without a dark dip in the middle
When a story moves from day to evening, fading one picture out while the other fades in often leaves a dark, muddy moment half-way, as if a cloud passed. The cause is simple, and so is the cure. Here is what to fade and what to leave alone, and one more trap with colour.
Shake the screen so heavy hits feel heavy and many small hits do not make it unplayable
Random jitter each frame looks like a broken screen, a fixed pattern looks fake, and a long fight with many hits can shake the picture until nothing is readable. Here is a shake that grows with the impact, fades out by itself, moves smoothly and stays within a limit.