Technical requirements

  • We currently support all recent versions of Chrome, and Firefox versions 47 and higher. We plan to support Internet Explorer 11 and Edge as soon as possible, but we're not there yet.
  • It's highly recommended, but not required, to play with a mouse and laptop/desktop. We don't think the game will work well on a touchpad, but we'd like to hear about your experiences if you try it.
  • We don't currently support mobile devices or touchscreens, but we hope to in the future.

Hints for common problems

  • Created account, but unable to log in: check the email you registered your account with. You should have received an activation link. Click the activation link to activate your account and log in.
  • The game loses my place when I go to another part of the site or close and reopen the page: make sure you have cookies enabled.

Keyboard Shortcuts

  • V : Switch to Virtual Finger tracing mode
  • C : Switch to Connect-the-Dots tracing mode
  • D : Switch to Delete Single Node mode
  • B : Switch to Delete Branch mode
  • U : Undo trace or delete action
  • R : Redo trace or delete action
  • A : Toggle auto z-adjustment for Connect-the-Dots tracing
  • Ctrl and [, then F5 (or reload page): Restarts tutorial from the beginning
  • Ctrl and ], then F5 (or reload page): Automatically completes tutorial
  • H : Cycles through the combinations of your traces being fully visible vs hidden and consensus being fully visible vs hidden
  • Arrows ←↑↓→ (all computers) OR 4, 8, 2 and 6 on Num Pad with Num Lock off (PC only): Translate current view
  • Shift and Right Mouse Button click/hold and drag: Another way to translate view(moves view in direction of mouse drag)
  • Spacebar : Re-centers the view along X, Y and Z axis, and focuses on the front of the challenge
  • F : Fullscreen toggle
  • Google Chrome, Mozilla Firefox and Internet Explorer (when in Fullscreen mode): Ctrl and + / Ctrl and -: Increases / decreases the font size


Thank you so much for trying our beta. This stage of beta is an open beta, so be sure and tell your friends about Mozak. Our current goal is to be able to give Mozak players (non-experts) the tools needed to construct expert-level neuron reconstructions.

Here are some things you can do to help us reach this important goal:

  • We need you to trace as much of the neuron as possible.
  • You can submit your bugs here. For maximum helpfulness, please include browser version, operating system, and any error messages you receive; if you want help gathering that information, check here.
  • You can submit suggestions here to help us make Mozak more awesome and fun; after all, we're trying to make a game people will enjoy while helping advance science. Strive to be honest but constructive. We've got plenty of things on our list already (we're all gamers in our spare time), but even if you make a suggestion you've already thought of, your input helps us prioritize future work.
  • We're a small team, but our enthusiasm is mighty. Your patience is appreciated.

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How to Play: Navigational Tools

Each neuron in Mozak is a single, extremely large, image — so large that your computer would never be able to load the whole thing at once. Mozak cuts it down to size by allowing you to see small parts of the image in full detail, but also letting you view less-detailed versions of the image from farther away, so you can get a better idea what's going on on a larger scale.

Change Resolution

The plus button at the top of the screen allows you to zoom into the image and increase its resolution so you can see finer details. Click the plus button, and a box will appear; that box is the section of the image you'll be able to view after zooming in. Click again to actually zoom.

The minus button lets you go back to a lower-resolution image. Click the minus button and you'll zoom back out. If you want to zoom out all the way, you can click the "min" button to do that in one click.

If you want to change resolutions even faster, there are helpful shortcuts. A double left-click acts like you clicked the plus button and then centered the zoom box on your cursor; a double right-click acts like you clicked the minus button.

Zoom In/Out

If you want to zoom in or out without changing the resolution, use your mouse's scroll wheel.

Translate Camera

In order to look at a different section of the image, use the green and red arrows on the edges. Your view will move in the direction the arrow is pointing. You can also move this section of the image on the screen with the arrow keys.

Rotate Camera

To view the neuron from a different perspective, hold and drag with your right mouse button. This is helpful when you feel like you've completed a section and want to view it from another angle, or when you want to get a better look at details that are hidden behind other parts of the neuron.

Invert Colors

Click the invert tool toward the top of the tools menu. This will invert the colors, which may help you identify difficult-to-see sections. If you've inverted the colors, your bounding box will change color from yellow to purple so you can see it better on a light background.

Adjust Contrast

Another tool that will help you see difficult-to-see sections is the contrast slider at the top of the screen. Drag it to the right to make the image lighter, to the left to make it darker.

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How to Play: Tracing Tools

The neuron reconstructions you build in Mozak are made of a skeleton of nodes (which appear as red dots), connected by lines. You can also view the reconstructions that other players have made — their nodes appear as light blue dots.

Virtual Finger

By default, you're in Virtual Finger mode. Simply hold your left mouse button while dragging your cursor along a branch of the neuron, then release and the computer will automatically follow it. This is the tool you'll use for most of your tracing.

If you move your mouse near a part of the neuron you've already reconstructed, you can highlight a node to extend from, which will make its node appear larger. When you extend from a node with Virtual Finger, the start of the branch you trace will be connected to that node.

After you start tracing, if you move your mouse near a part of your reconstruction, you can highlight a node to connect to, which will draw a blue highlight around it. When you connect to a node with Virtual Finger, the end of the branch you trace will be connected to that node.

Connect-the-dots mode

Some parts of the neuron are too dim to trace with Virtual Finger. When you select the connect-the-dots tool, you shift from a 3D view of the neuron to seeing a single 2D z-slice through the neuron, somewhere between its front and its back. In this view, an individual neuron branch looks like a series of bright spots and lines on neighboring z-slices.

You can move between slices by rolling your mouse wheel up and down. When you see one of these bright spots, you can place a node on it by left-clicking, and build up a branch by following the branch between planes and dropping nodes in a line as you go. Right-click when you're done with a given branch to put those nodes into your reconstruction, and once you're completely done with connect-the-dots, click the button again to switch back to Virtual Finger.

Delete Node/Branch

Sometimes you'll make mistakes, but you can fix them. For small mistakes, select the eraser tool, then left-click to delete a single node.

For bigger mistakes, you can delete a whole branch at a time. Select the trash tool, then left-click on the branch to delete.

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How to Play: Common Errors/Mistakes


Z-jumps happen when Virtual Finger gets confused about what z-slice a branch is on. It creates a segment that inappropriately stretches between z-slices that are great distances away. You can use the delete tool and delete single nodes to fix this issue.

Tracing False Positive

Sometimes you will encounter strands that look like a part of the neuron but are not really. These are false positives and should be avoided as the scientists need to cleanup/remove them during their evaluation. As a rule of thumb, if the strand you are looking at does not eventually connect back to the main neuron structure you should avoid tracing it.

Comment area looks empty

If the bounding box marked by a comment looks like it's empty, try using Connect-the-Dots mode to look through each z-slice for things you can't see in 3D. If you still can't see anything, try inverting colors or dragging the contrast slider to get a better look. Use the H key to turn off consensus traces if those are interfering.

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