Nature and effects
Learning paths through this topic
Float a lantern or a body down a river that is fastest in the middle and snags on the bank
A boat of paper or something worse carried down a river is a classic story beat, and an object that moves at one speed across the whole width looks like a conveyor belt. A real river is quick in the middle, slow at the banks and pulls things sideways on bends. Here is how to get a drift that can end in the reeds.
Draw a jagged lightning bolt with a double flash and thunder that arrives late
A storm level needs lightning that looks different every time and is still easy to test. A straight line is dull, a random scribble is wrong, and thunder at the same instant as the flash feels cheap. Here is a way to build a bolt from a seed, light the sky like the real thing flickers, and delay the rumble by distance.
Show lightning as a double flash and let the thunder arrive later by distance
A single white frame looks like a glitch, and thunder that plays at the same moment as the flash makes every storm feel like it is right on top of you. Here is how a strike really reads on screen, and how to let the player judge by ear how close the danger is.
Make the liquid in a bottle slosh and tilt when the bottle is dragged
In a pouring puzzle the liquid should sway and wobble as the player drags the bottle, not stay as a flat bar. A surface that follows the drag instantly looks stiff, one that spills over the edge of the glass breaks the picture. Here is a small spring that sloshes with weight and always stays inside the bottle.
Stretch shadows at dusk without them running off the screen at sunset
Long shadows at dusk are one of the cheapest ways to make a scene feel uneasy, but the plain maths gives a shadow of endless length just as the sun touches the horizon, and then it jumps away when the sun sets. Here is how to keep the mood and avoid both the blow-up and the jump.
Make an ice block melt so its size and the puddle both look right
A timer says how much ice is left, and the picture has to follow. Scale the sprite by that number and it seems to shrink far too fast, then hang around as a speck at the end. The puddle has the opposite problem. Here is the maths that makes both look natural and when to call it gone.
Scroll layers of mist at different speeds so the picture never shows a seam
Drifting mist over a lake at dawn is a favourite backdrop for a quiet scene, and it is easy to ruin: a gap appears when the picture ends, the layers move in lockstep, or the picture jumps whenever the camera crosses an edge. Here is the small piece of arithmetic that prevents all three.
Show the right moon for any story day, also days before the story began
A werewolf night needs a full moon on the right day, and a player who skips ahead or reads a flashback must see the right moon too. A moon that just loops by frame count drifts away from the story. Here is how to tie it to the calendar, and what breaks on the first days.
Show the right moon phase for today's date, with the curved edge of the light
A calm night scene gets a nice touch when the moon matches the real calendar or your invented world's calendar. The numbers are simple, but the pictures are often wrong: the lit part drawn as a straight cut, the waxing and waning mixed up, or the phase jumping at midnight. Here is the small maths behind it.
Tint the moon from white to deep red as it sinks, and darker still in an eclipse
A moon that stays white all night is a missed chance for a dread-soaked scene: low on the horizon it is orange, and in a story eclipse it should be the colour of a wound. Choosing the tints by eye gives muddy results. Here is the physical reason, a simple formula that follows it, and how to avoid its blow-up at the horizon.
Let night animals appear in the evening and leave at dawn, across midnight
Owls, fireflies and foxes should only show up at night, and day creatures the other way round. A window from evening to morning breaks the obvious check, because it wraps past midnight, and animals that appear in a single frame look like a mistake. Here is an activity value that works for any window and fades at its edges.
Make an owl follow a sound with its head first, then turn its body for the rest
An owl on a branch that watches the player is a perfect horror prop, and the two usual mistakes both spoil it: the whole bird swivels like a turret, or the head spins a full circle the wrong way. Here is how to split the turn between head and body, keep the gaze steady, and make a quick snap.