Movement personalities — one dot, eight souls

Personality is not what moves — it's the shape of the speed. Edit the personality string on the first line (human, superhuman, alien, excited, sad, emotionless, robot, stately), press Run, and watch the same journey change species.

let personality = "human";   // ← edit me, then press Run

// Each personality maps u (journey progress 0→1)
// to {x: 0→1 across, y: vertical detour}.
const P = {
  human(u){        // ease both ends + gentle bob
    const e = u < .5 ? 4*u*u*u : 1 - Math.pow(-2*u+2, 3)/2;
    return { x: e, y: Math.sin(u*Math.PI*2.2)*0.06 };
  },
  superhuman(u){   // anticipation pull-back, then t^4 snap
    if (u < 0.25) return { x: -0.05*(u/0.25), y: 0 };
    if (u < 0.45) { const t=(u-.25)/.2; return { x: -0.05+1.05*t*t*t*t, y: 0 }; }
    return { x: 1, y: 0 };
  },
  alien(u){        // drift + abrupt reorientation, unsynced sines
    let y = 0.35*Math.sin(u*6.28) + 0.25*Math.sin(u*6.28*1.618+2);
    if (Math.floor(u*5) % 2 === 1) y = -y*0.6;
    return { x: Math.min(1, u + 0.06*Math.sin(u*13)), y: y*0.5 };
  },
  excited(u){      // springy overshoot with bounces
    const e = 1 - Math.pow(2, -8*u) * Math.cos(u*14);
    return { x: Math.min(1.06, e), y: -Math.abs(Math.sin(u*12))*0.22*(1-u) };
  },
  sad(u){          // hesitate... then droop through a sagging arc
    if (u < 0.22) return { x: 0, y: 0.05 };
    const t = (u-0.22)/0.78, e = 1 - Math.pow(1-t, 2.6);
    return { x: e, y: 0.05 + Math.sin(t*Math.PI)*0.28 };
  },
  emotionless(u){  // pure linear. that's the whole recipe.
    return { x: u, y: 0 };
  },
  robot(u){        // 7 quantised steps + tiny servo settle
    const steps=7, s=Math.floor(u*steps)/steps, f=(u*steps)%1;
    const settle = f<0.3 ? Math.sin(f/0.3*Math.PI*3)*Math.exp(-f*10)*0.015 : 0;
    return { x: s+settle, y: 0 };
  },
  stately(u){      // long sine ease + wide unhurried arc
    const e = -(Math.cos(Math.PI*u)-1)/2;
    return { x: e, y: -Math.sin(u*Math.PI)*0.42 };
  }
};
const dur = { human:2, superhuman:2.2, alien:3.4, excited:2.4,
              sad:3.6, emotionless:2.4, robot:3, stately:4.2 };

const pad=40, midY=H*0.55, amp=H*0.3, trail=[];
onFrame((dt, t) => {
  const u = Math.min(1, t / dur[personality]);
  const p = P[personality](u);
  trail.push(p); if (trail.length > 120) trail.shift();
  ctx.clearRect(0, 0, W, H);
  ctx.strokeStyle = "#88888855"; ctx.setLineDash([2,5]);
  ctx.beginPath(); ctx.moveTo(pad,midY); ctx.lineTo(W-pad,midY);
  ctx.stroke(); ctx.setLineDash([]);
  ctx.fillStyle = "#5A63C8";
  trail.forEach((q, i) => {           // fading breadcrumb trail
    ctx.globalAlpha = 0.05 + 0.1*(i/trail.length);
    ctx.beginPath();
    ctx.arc(pad+q.x*(W-2*pad), midY+q.y*amp, 4, 0, 7); ctx.fill();
  });
  ctx.globalAlpha = 1;
  ctx.beginPath();
  ctx.arc(pad+p.x*(W-2*pad), midY+p.y*amp, 9, 0, 7); ctx.fill();
});

The breadcrumb trail is the personality made visible: evenly spaced crumbs = constant speed (emotionless); bunched-then-spread = acceleration; a sagging path = sorrow.

Try tweaking: in excited, change -8 (damping) to -3 — more bounces, more mania · in robot, change steps=7 to 3 · in stately, double the duration in dur and feel the extra dignity · invent a ninth personality by copying any entry and breaking one rule.

In Godot: the built-in Tween runs these same recipes — download personalities.gd from the Godot project. In Unity: DOTween's SetEase covers half of these; the spring and quantise recipes drop into Update(). In Unreal: Timeline curves — drawing these shapes by hand in the curve editor is drawing the personality. Chapter 05 has all of it.