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Image occlusion

Masks (hides) specific regions on an image, and you try to recall what's hidden. Useful for memorizing labels on a diagram, locations on a map, or parts of a schematic.

Fields​

  • Title: a short text shown above the flash that identifies the card.
  • Image + mask fields: the image you upload, and the mask shapes you draw on it.
  • Extra info (backExtra): optional additional explanation that appears after the answer is shown.

Mask shapes and groups​

You draw mask fields on the image as rectangles, circles, triangles, pentagons, or hexagons. Each field belongs to a group; fields that share a group are studied together as a single flash. In other words:

  • If you draw five separate label masks on an image and put each one in a different group, five separate flashes are generated (only one is hidden at a time).
  • If you put several masks in the same group, that group becomes a single flash (they're all hidden/shown together).

You can set each mask field's own color, rotation, and stacking order (z-index) independently.

View mode​

Two modes determine what happens to the other masks (the ones not in the flash's group) while you study a flash:

  • Only the active group hidden: the group you're studying is masked, and every other group is shown openly (helpful as context).
  • All hidden: every group is masked, including the one you're studying.

This can be set as a general default in settings, and overridden on a per-card basis as well.

Example​

If you upload a diagram of a cell, draw three separate masks over the mitochondrion, the nucleus, and the cell membrane, and put each in a different group, three separate flashes are generated: each flash hides one organelle in turn, and you answer "what is this."

Tips​

  • Masking a very small area (like a single thin line) can be hard both to draw and to locate in the image; keep the mask large enough to comfortably cover the target region.
  • Grouping several related labels together (like all the parts of one organ) lets you test them together on a single flash; if you'd rather test them separately, put them in separate groups.

Good and bad examples​

In this card type, the fields are filled in by drawing, not by typing; the blocks below aren't literal syntax, just a descriptive summary of which labels are in which group.

✅ Good (each label in its own group):

Image: Neuron diagram
- Group 1: "Dendrite" label
- Group 2: "Axon" label
- Group 3: "Cell body" label

Three separate flashes are generated, each asking about a single part. You can clearly see which one you know and which one you don't.

❌ Bad (grouping different concepts into one group):

Image: Neuron diagram
- Group 1: "Dendrite" + "Axon" + "Cell body" (all three in the same group)

Three different parts are hidden/asked together on one flash. Even if you know two of them and not the third, the flash only gets a single "I know it/I don't know it" grade; you can't tell which one you actually haven't learned.