Random numbers

You want a bit of luck in the game: enemies at different positions, an item that sometimes shows up.

vspeed = random(0.8f, 1.6f);                 // a decimal number between 0.8 and 1.6
const int lane = randomInt(1, 3);            // 1, 2 or 3
if (chance(0.1f)) spawn<PowerUp>(x, y, "Instancias");      // 10% chance
sprite = pick("inimigo_verde", "inimigo_roxo"); // one of the two

How it works

Function	What it picks
`random(a, b)`	A decimal number, from `a` up to almost `b`.
`randomInt(a, b)`	A whole number from `a` to `b`, including both.
`chance(p)`	`true` with probability `p`: `0.25f` is 25%.
`pick(a, b, c...)`	One of the values you pass.

Variation: the same result every time

To test a level, sometimes you want the “random” to repeat itself exactly. Fix the seed at the start:

randomSeed(42);

With the same seed, the sequence of random results is always the same.

See also

Math and random.