KNIFE SPIN:
A THREE.JS KNIFE THROWING GAME

What Is Knife Spin?

Knife Spin is a free portrait 3D knife throwing game for phones and desktop. Tap to throw knives into the spinning log, slice apples for bonus points and clear each stage when your knives run out. Spin speeds and reversals change every stage, and every 5th stage is a boss log. Your best score is saved on your device.

It is a Three.js game that runs as a 3D browser game on WebGL, developed by Shane Brumback and hosted by Indie Forge Studio. It is free with no download or sign-up.

How to Play Knife Spin

• Throw: tap (or press Space) to throw a knife into the spinning log.
• Avoid stuck knives: if your knife hits a knife already in the log, the run is over.
• Slice apples: hit an apple on the rim for 5 bonus points.
• Clear the stage: use all your knives and the log shatters, giving a stage bonus.
• Beat bosses: every 5th stage is a big red boss log with erratic spin and more knives to land.

Controls: Phones: tap anywhere to throw · Desktop: Space or Enter · P pause · M mute

How Knife Spin Is Built with Three.js

Knife Spin is plain JavaScript with no build step. It loads Three.js r160 as an ES module from a local copy of three.module.min.js and draws everything with a single THREE.WebGLRenderer. All the 3D models are built in code from Three.js primitives, so there are no 3D model files to download. Here is what the game code actually does:

• The log is a 13-sided CylinderGeometry rotated to face the camera, with a CircleGeometry face, all inside a group that spins each frame.
• Each knife is a THREE.Group: a ConeGeometry blade flattened with geometry.scale, plus box meshes for the guard and handle.
• When a knife sticks, it is added to the spinning log group at its angle on the rim, so it turns with the log. A hit is decided by comparing that angle with the knives already there.
• Apples are low-poly IcosahedronGeometry meshes. Slices and stage clears throw out bursts of small TetrahedronGeometry pieces.
• Sound effects are made on the fly with the Web Audio API (AudioContext oscillators) instead of audio files, and your best score and mute setting are stored in localStorage.

Code from Knife Spin

These short snippets are copied straight from the game's source code.

Sticking a knife into the log

A stuck knife is placed on the rim at its angle and added to the spinning group, so it turns with the log.

function stickAt(a) { const m = makeKnife(); m.position.set(Math.cos(a) * (R + 0.55), Math.sin(a) * (R + 0.55), 0); m.rotation.z = a + Math.PI / 2; spinner.add(m); S.stuck.push({ a, mesh: m }); }

From games/knife-spin/game.js, lines 62–62

Hit or clash

When a knife arrives, its angle on the log is compared with every stuck knife. Too close is a clash and game over; otherwise it sticks and the score goes up.

function hit() {
  const k = S.flying; const local = norm(-Math.PI / 2 - spinner.rotation.z);
  for (const s of S.stuck) if (Math.abs(norm(s.a - local)) < 0.2) { // clash
    k.dead = true; k.vy = -10; k.vx = (Math.random() - 0.5) * 6; k.spin = 14; S.shake = 0.4;
    core.beep(1400, 0.08, 'square', 0.06); core.beep(200, 0.3, 'sawtooth', 0.07, -120); core.gameOver(); return;
  }
  scene.remove(k.mesh); S.flying = null; stickAt(local); S.left--; S.shake = 0.12;

From games/knife-spin/game.js, lines 79–85

Touch and mouse input (shared core.js)

One pointerdown listener on the game frame handles taps and clicks alike, ignoring the pause and mute buttons, and wakes the Web Audio context on the first touch.

  frame.addEventListener('pointerdown', (e) => { if (e.target.closest('.icon-btn')) return; C.audio(); e.preventDefault(); primary(e); });

From games/knife-spin/core.js, lines 51–51

Built for Mobile and Portrait Play

Knife Spin is designed for phones held upright. The game runs in a 9:16 portrait frame, and on desktop it plays in a centered portrait frame. Input uses pointer events, so the same code handles touch and mouse, with keyboard controls on desktop.

To keep it smooth on phones, the renderer caps the device pixel ratio, and the game pauses itself when you switch tabs or apps. Phones that support it give a short vibration as feedback.

Frequently Asked Questions