Isle-Slingers/test/landedbird.test.mjs

// test/landedbird.test.mjs -- landed bird remains a physical body.
// Design spec (verbatim): "When a board is broken from underneath a bird it just
// floats. Gravity needs to work for the birds as well so if the platform falls
// from underneath them they can fall causing more damage to any boards that they
// fall on like a chain reaction and the birds can also kill more enemy's that way
// as well. That is AFTER a bird has been shot from a slingshot and another bird is
// already active."
// Q2 (ruling): REAL CONTINUOUS GRAVITY, no fixed lifetime timer -- the
// bird is a body as long as it exists.
//
// The pre-S-5 defect: spendBird() marked a settled bird 'spent' and zeroed its
// velocity; stepPhysics only integrated the ACTIVE bird, so a settled bird was a
// visual corpse -- when its platform broke it FLOATED in place (never fell).
import { createRequire } from 'node:module';
const require = createRequire(import.meta.url);
const ISLE = require('../js/physics/index.js');

const DT = 1 / 120;
let passed = 0, failed = 0;
function check(name, cond, detail) {
  if (cond) { passed++; console.log('  PASS ' + name); }
  else { failed++; console.log('  FAIL ' + name + (detail ? ' -- ' + detail : '')); }
}
function game(def) {
  const lvl = Object.assign({ name: 'lb-test', sling: { x: 260, y: 560 }, birds: [], blocks: [], enemies: [] }, def);
  return ISLE.createGame(lvl);
}
function step(g, secs) {
  const n = Math.round(secs / DT);
  for (let i = 0; i < n; i++) ISLE.step(g, DT);
}
// helper: put a bird in a settled/landed state on a board, with a queued second
// bird active (the "another bird is already active" window).
function setupPerched() {
  // board 200x30 at (1200,765): x 1100..1300, top 750.
  const g = game({
    blocks: [{ x: 1200, y: 765, w: 200, h: 30, mat: 'wood' }],
    birds: ['wren', 'wren'],   // [0] will be perched, [1] the 'already active' next bird
  });
  // bird 0: perched on the board, settled (no velocity).
  const b0 = g.birds[0];
  b0.state = 'landed';
  b0.x = 1200; b0.y = 750 - b0.r;   // resting on the board top
  b0.vx = 0; b0.vy = 0;
  // bird 1: active, aiming on the sling.
  g.activeBird = 1;
  g.birds[1].state = 'aiming';
  g.birds[1].x = g.level.sling.x; g.birds[1].y = g.level.sling.y;
  return g;
}

// arm 1 (THE S-5 behaviour): the perched bird FALLS when its board breaks.
// The board rests on two stone pillars (so the platform is stable); the bird
// is perched on the board. A bird that is a corpse (pre-S-5) would stay at its
// perch forever while the board falls away. The landed bird must drop toward
// the ground (y rises well past the perch).
{
  const g = game({
    blocks: [
      { x: 1120, y: 840, w: 40, h: 120, mat: 'stone' },  // pillar L (top 780)
      { x: 1280, y: 840, w: 40, h: 120, mat: 'stone' },  // pillar R (top 780)
      { x: 1200, y: 765, w: 200, h: 30, mat: 'wood' }    // board 750..780 on the pillars
    ],
    birds: ['wren', 'wren']
  });
  const b0 = g.birds[0];
  b0.state = 'landed';
  b0.x = 1200; b0.y = 750 - b0.r;
  b0.vx = 0; b0.vy = 0;
  g.activeBird = 1; g.birds[1].state = 'aiming';
  g.birds[1].x = g.level.sling.x; g.birds[1].y = g.level.sling.y;
  const board = g.blocks[2];
  step(g, 0.5);
  const yIntact = b0.y;
  board.hp = 0;   // break the board out from under the bird
  step(g, 2.0);
  check('perched bird FALLS when its platform breaks (Q2 real gravity)', b0.y > yIntact + 80,
    'y intact=' + yIntact.toFixed(0) + ' -> after break=' + b0.y.toFixed(0) + ' (ground=' + ISLE.WORLD.ground + ')');
}

// arm 2: a landed bird on a stable board (pillars + board) does NOT drift.
{
  const g = game({
    blocks: [
      { x: 1120, y: 840, w: 40, h: 120, mat: 'stone' },
      { x: 1280, y: 840, w: 40, h: 120, mat: 'stone' },
      { x: 1200, y: 765, w: 200, h: 30, mat: 'wood' }
    ],
    birds: ['wren', 'wren']
  });
  const b0 = g.birds[0];
  b0.state = 'landed';
  b0.x = 1200; b0.y = 750 - b0.r;
  b0.vx = 0; b0.vy = 0;
  g.activeBird = 1; g.birds[1].state = 'aiming';
  g.birds[1].x = g.level.sling.x; g.birds[1].y = g.level.sling.y;
  const x0 = b0.x, y0 = b0.y;
  step(g, 2.0);
  check('landed bird on an intact board stays put (no drift, no float-away)', Math.abs(b0.x - x0) < 2 && Math.abs(b0.y - y0) < 3,
    'x ' + x0.toFixed(1) + '->' + b0.x.toFixed(1) + '  y ' + y0.toFixed(1) + '->' + b0.y.toFixed(1));
}

// arm 3 (chain reaction): the falling bird damages the board it lands on.
// Bird perched high, board beneath it breaks, a lower board catches it -- the
// lower board must take impact damage.
{
  const g = game({
    blocks: [
      { x: 1200, y: 600, w: 120, h: 30, mat: 'ice' },   // upper perch (breaks)
      { x: 1200, y: 880, w: 200, h: 40, mat: 'ice' }    // lower catcher
    ],
    birds: ['wren', 'wren']
  });
  const b0 = g.birds[0];
  b0.state = 'landed';
  b0.x = 1200; b0.y = 585 - b0.r;   // on the upper perch top (585)
  b0.vx = 0; b0.vy = 0;
  g.activeBird = 1;
  g.birds[1].state = 'aiming';
  g.birds[1].x = g.level.sling.x; g.birds[1].y = g.level.sling.y;
  const catcher = g.blocks[1];
  const catcherHp0 = catcher.hp;
  g.blocks[0].hp = 0;   // break the perch
  step(g, 2.0);
  check('falling bird damages the board it lands on (chain reaction)', catcher.hp < catcherHp0,
    'catcher hp ' + catcherHp0 + ' -> ' + catcher.hp.toFixed(0));
}

// arm 4 (kill): the falling bird can kill an enemy in its fall path.
{
  const g = game({
    blocks: [{ x: 1200, y: 600, w: 120, h: 30, mat: 'ice' }],
    enemies: [{ x: 1200, y: 876, kind: 'mogg' }],
    birds: ['wren', 'wren']
  });
  const b0 = g.birds[0];
  b0.state = 'landed';
  b0.x = 1200; b0.y = 585 - b0.r;
  b0.vx = 0; b0.vy = 0;
  g.activeBird = 1;
  g.birds[1].state = 'aiming';
  g.birds[1].x = g.level.sling.x; g.birds[1].y = g.level.sling.y;
  const e = g.enemies[0];
  g.blocks[0].hp = 0;   // break the perch -> bird drops onto the mogg
  step(g, 2.5);
  check('falling bird KILLS an enemy in its fall path', e.dead,
    'mogg hp=' + e.hp + ' dead=' + e.dead + ' birdY=' + b0.y.toFixed(0));
}

console.log('== ' + passed + ' passed, ' + failed + ' failed ==');
process.exit(failed ? 1 : 0);