<!-- SAGA3 · part 42 -->

  window._dynamics = window._dynamics || [];
  window._dynamics.push(function(){
    try{
      var now = performance.now();
      var dt = now - lastT;
      lastT = now;
      frameTimes.push(dt);
      if(frameTimes.length > 60) frameTimes.shift();
      if(frameTimes.length === 60){
        var avg = frameTimes.reduce(function(a,b){return a+b;}, 0) / 60;
        var fps = 1000 / avg;
        var pr = renderer.getPixelRatio();
        if(fps < 25 && pr > 0.6){
          renderer.setPixelRatio(Math.max(0.6, pr - 0.1));
        } else if(fps > 50 && pr < 1.25){
          renderer.setPixelRatio(Math.min(1.25, pr + 0.05));
        }
        frameTimes = [];
      }
    }catch(e){}
  });
})();

/* BRIDGE-TUNNEL HYBRID — Aqua-Line model. Bridge dives into tunnel. 2026-10-04. */
function buildAquaLine(){
  try{
    var concreteMat = new THREE.MeshStandardMaterial({color: 0x888888, roughness: 0.8});
    /* Bridge section: from shore */
    var bridge = new THREE.Mesh(new THREE.BoxGeometry(12, 3, 400), concreteMat);
    bridge.position.set(2900, 8, 500);
    scene.add(bridge);
    /* Pillars */
    for(var p = 0; p < 8; p++){
      var pillar = new THREE.Mesh(new THREE.CylinderGeometry(3, 4, 16, 8), concreteMat);
      pillar.position.set(2900, 0, 320 + p*50);
      scene.add(pillar);
    }
    /* Artificial island (Umihotaru) */
    var island = new THREE.Mesh(new THREE.CylinderGeometry(40, 45, 6, 16), concreteMat);
    island.position.set(2900, 2, 720);
    scene.add(island);
    var tower = new THREE.Mesh(new THREE.CylinderGeometry(8, 10, 30, 8), concreteMat);
    tower.position.set(2900, 18, 720);
    scene.add(tower);
    /* Tunnel portal — dives underwater */
    var portal = new THREE.Mesh(new THREE.BoxGeometry(16, 12, 4), concreteMat);
    portal.position.set(2900, 2, 745);
    scene.add(portal);
    var dark = new THREE.Mesh(new THREE.PlaneGeometry(12, 8),
      new THREE.MeshBasicMaterial({color: 0x000000}));
    dark.position.set(2900, 2, 747.1);
    dark.rotation.y = Math.PI;
    scene.add(dark);
  }catch(e){}
}
if(typeof buildAquaLine === 'function'){ try{ buildAquaLine(); }catch(e){} }

/* TRANSITION BANDS — blend zones between districts, not hard borders. 2026-10-04. */
function buildTransitions(){
  try{
    /* Gradient strips where city meets forest, desert meets water, etc. */
    function blendZone(x1, z1, x2, z2, c1, c2){
      var dx = x2 - x1, dz = z2 - z1;
      var len = Math.sqrt(dx*dx + dz*dz);
      var segs = 10;
      for(var i = 0; i < segs; i++){
        var t = i / (segs - 1);
        var px = x1 + dx * t;
        var pz = z1 + dz * t;
        /* Lerp color */
        var r = ((c1 >> 16) & 255) * (1-t) + ((c2 >> 16) & 255) * t;
        var g = ((c1 >> 8) & 255) * (1-t) + ((c2 >> 8) & 255) * t;
        var b = (c1 & 255) * (1-t) + (c2 & 255) * t;
        var col = (Math.round(r) << 16) | (Math.round(g) << 8) | Math.round(b);
        var strip = new THREE.Mesh(new THREE.PlaneGeometry(40, len/segs + 2),
          new THREE.MeshStandardMaterial({color: col, roughness: 0.9, transparent: true, opacity: 0.7}));
        strip.rotation.x = -Math.PI/2;
        strip.position.set(px, 0.3, pz);
        strip.rotation.z = Math.atan2(dx, dz);
        scene.add(strip);
      }
    }
    /* City (gold) -> Forest (green) */
    blendZone(100, -50, -50, 50, 0xd4a017, 0x1a5a1a);
    /* Desert (sand) -> Ocean (blue) */
    blendZone(800, 1400, 1200, 800, 0xd4b896, 0x0088cc);
    /* Village (warm) -> Peaks (white) */
    blendZone(-80, 250, -500, -500, 0xd4c4a0, 0xffffff);
  }catch(e){}
}
if(typeof buildTransitions === 'function'){ try{ buildTransitions(); }catch(e){} }

/* FREIGHT PORTALS — underground cargo network entrances. 2026-10-04. */
function buildFreight(){
  try{
    var darkMat = new THREE.MeshStandardMaterial({color: 0x1a1a1a, roughness: 0.9});
    function portal(x, z){
      /* Ramp going down */
      var ramp = new THREE.Mesh(new THREE.BoxGeometry(12, 2, 30), darkMat);
      ramp.position.set(x, -2, z);
      ramp.rotation.x = 0.2;
      scene.add(ramp);
      /* Portal frame */
      var frame = new THREE.Mesh(new THREE.BoxGeometry(14, 10, 2), darkMat);
      frame.position.set(x, 3, z - 14);
      scene.add(frame);
      /* Opening */
      var opening = new THREE.Mesh(new THREE.PlaneGeometry(10, 7),
        new THREE.MeshBasicMaterial({color: 0x000000}));
      opening.position.set(x, 3, z - 12.9);
      scene.add(opening);
      /* Warning lights */
      for(var l = -1; l <= 1; l++){
        var light = new THREE.Mesh(new THREE.SphereGeometry(0.5, 8, 6),
          new THREE.MeshBasicMaterial({color: 0xff0000}));
        light.position.set(x + l*6, 8.5, z - 12.8);
        scene.add(light);
      }
    }
    portal(150, -100);
    portal(-130, 180);
    portal(2050, 2000);
  }catch(e){}
}
if(typeof buildFreight === 'function'){ try{ buildFreight(); }catch(e){} }

/* DISTRICT CENTERS — plazas at the heart. 2026-10-04. */
function buildPlazas(){
  try{