Levels and difficulty

A level is a set of numbers that tells a game how hard to be. It says how fast things fall and how often a new one appears. A spawn schedule is the rule for when each new thing appears.

When levels are data, a designer changes a table and plays again, with no new code to write or break.

The lab's game keeps its levels in a list, one row for each. A row has a name, the score at which it starts, and two scales. One scales the gravity. The other scales how often stars appear.

The game finds the current level by looking down the list for the last row whose start the score has reached.

var LEVELS = [
  { name: "Drizzle", from: 0, gravityScale: 1.0, spawnScale: 1.0 },
  { name: "Shower", from: 5, gravityScale: 1.4, spawnScale: 1.25 },
  { name: "Storm", from: 12, gravityScale: 1.8, spawnScale: 1.6 },
  { name: "Meteors", from: 20, gravityScale: 2.4, spawnScale: 2.0 }
];

// A score of 7 has reached 0 and 5, but not 12, so the level is Shower.

docker exec jupyter python3 steps/levels.py

The script reads the table and the base numbers, GRAVITY of 0.15 and SPAWN_EVERY of 50. It prints four lines, one for each level.

Drizzle has gravity 0.150 and a star every 50 frames. Shower has 0.210 and every 40. Storm has 0.270 and every 31. Meteors has 0.360 and every 25. The gap is 50 divided by the scale, rounded to a whole frame.

The game counts frames. A star spawns on a frame when the frame number divides exactly by the gap. In Python and in JavaScript, the remainder of a division is written %, so the test is frame % gap == 0.

With a gap of 40, stars spawn on frames 40, 80, 120 and so on. When the level changes, the gap changes, and the next test uses the new gap.

The table assumes a screen that draws 60 frames a second. It shows the stars doubling from 12 to 24 across four levels, while gravity rises from 0.15 to 0.36.

A good curve rises in steps a player can meet. If one level doubled everything at once, players would stop there and not know why.