Small interactive activities
Try it.
Then it clicks.
Explore a computing or security idea by trying it. Start with something familiar, make one change and see what happens.
What are you curious about?
Pick an activity. Each one explains the idea and gives you a small task.
Count with switches
Turn a few switches on. Add their numbers.
↘02 / NetworkingSend a message
Choose a path and watch a message travel.
↘03 / SecurityWho gets access?
Choose who may read school information.
↘04 / NetworkingJoin the dots
Make a path from every dot to the center.
↘05 / ComputingHow computers store text
Compare the space used by a letter and an emoji.
↘06 / ComputingMix a screen color
Slide red, green and blue to make a color.
↘07 / ComputingHow long will it download?
Try a bigger file or a faster connection.
↘08 / NetworkingMake smaller neighborhoods
Split a group of addresses into equal parts.
↘09 / NetworkingRemember a website address
See why a saved address can become out of date.
↘10 / NetworkingStart a conversation
Put three short messages in order.
↘11 / SecurityWhich rule comes first?
Reorder rules at a pretend digital gate.
↘12 / SecurityAdd another kind of check
Compare a password with something you carry.
↘13 / SecuritySpot a tricky message
Find four reasons to stop and check.
↘14 / SecurityGive a message a fingerprint
Change one letter and compare the results.
↘15 / SecurityFind a copy that survives
Choose a backup after something goes wrong.
↘16 / SecurityWhat needs protecting?
Think about privacy, correct information and access.
↘01 / Computing
Count with switches
Imagine a row of light switches. Each one is either off (0) or on (1). Computers call one of these tiny on-or-off choices a bit.
Try this Turn on 4 and 2. Their numbers add up to 6. Then try making a different total.
Look for An on switch adds its number. An off switch adds nothing.
No switches are on, so the total is 0.
Build the number 6.
Turn on 4 and 2 to make 6.
The idea: A computer can build many numbers from simple on-or-off choices.
A little more detail +
Eight switches can show any whole number from 0 to 255. A group of eight bits is called a byte. Binary is a way to write numbers using only 0 and 1.
Reference: Internet Protocol (RFC 791) ↗02 / Networking
Send a message
Online messages travel in small pieces called packets. Think of a packet as a tiny parcel going from A to D. The numbers on each road show how long that part of the trip takes.
Try this Try all three paths. Which arrives fastest? Then close the C–E road and try that path again.
Look for One long road can be slower than several quick roads. A broken road stops the trip.
Choose a path to send a simulated packet.
The idea: A useful route must reach its destination. Fewer steps do not always mean a faster trip.
A little more detail +
Here the direct trip takes 80 milliseconds, the upper trip 34, and the lower trip 24. A millisecond is one thousandth of a second. These are made-up travel times; real networks choose routes using more information.
03 / Security
Who gets access?
A school has public news, private student records and computer settings. Everyone may read the news. Only the school office needs the private records. Nobody in this group manages the computer settings.
Try this Check only the boxes each person needs. Then choose “Check access.”
Look for Blocking everything stops useful work. Giving everyone everything exposes private information.
Give everyone the school news. Give only the office the private records.
The idea: Give the right people the right access for the job.
A little more detail +
Security professionals call this least privilege: give people the access needed for their task, with nothing extra. Like keys in a school, the right key should open only the right doors.
Reference: NIST, least privilege ↗04 / Networking
Join the dots
Think of the dots as computers and the lines as roads between them. Core is the center. Every dot needs a path back to it, even if that path goes through another dot.
Try this Select one dot, then another to draw a line. Keep going until every dot can reach Core. Use “Reset network” to start again.
Look for A group of dots can be joined to each other and still be cut off from the center.
The idea: Being connected means having a path to the place you need to reach.
A little more detail +
Try joining all twelve dots with just eleven lines. More lines can give you other paths. This small activity checks whether dots are connected; it does not copy all the ways a real network works.
05 / Computing
How computers store text
Computers store words and pictures as numbers. A byte is a small unit of storage. Some letters need one byte, while many emoji need several.
Try this Type A. Then try é and 🌎. Compare how many bytes each needs.
Look for One visible symbol can need more storage than another. The small number pairs show what the computer stores.
The idea: The space a message uses depends on its characters, not just how long it looks.
A little more detail +
UTF-8 is a shared rule for turning text into bytes. Some characters use more bytes than others, and a single visible emoji can combine several characters. You do not need to memorize these codes.
UTF-8 specification ↗06 / Computing
Mix a screen color
Screens mix red, green and blue light. Each slider controls how much of one color to add: 0 is none and 255 is the most.
Try this Move all three sliders to 0. Then move just red to 255. What changes when you add green?
Look for Red and green light together make yellow. All three at full strength make white.
The idea: A screen can make many colors by mixing three kinds of light.
A little more detail +
The code beginning with # is a short way to save your color. Its first pair controls red, the next green and the last blue. These pairs use digits 0–9 and letters A–F. You can explore the colors without memorizing the code.
CSS color notation ↗07 / Computing
How long will it download?
Imagine moving a box of blocks through a doorway. A bigger box takes longer; a wider doorway lets more through. File size is how much to move, and connection speed is how quickly it can move.
Try this Keep the file at 100 MB. Change the speed from 100 to 200 Mbps. Then try doubling the file size.
Look for Doubling the speed halves the ideal time. Doubling the file size doubles it.
100 MB × 8 ÷ 100 Mbps = 8 seconds.
The idea: File size and connection speed both affect how long a download takes.
A little more detail +
MB means megabytes, a way to measure file size. Mbps means megabits per second, a way to measure connection speed. There are eight bits in a byte, so the calculation is file size × 8 ÷ speed. Real downloads can take longer.
08 / Networking
Make smaller neighborhoods
Imagine 256 numbered houses. Move the slider to split them into equal neighborhoods. In a computer network, these smaller address groups are called subnets.
Try this Move the slider one step to the right. Then choose a different group below it.
Look for More groups means fewer addresses in each group. The first and last address in each group have special jobs.
The idea: Dividing one fixed space into more groups makes each group smaller.
A little more detail +
Each device needs an address, like a house number. A subnet gives a group its own range of addresses. In this example, the first identifies the group and the last can send a message to the whole group. The middle addresses are available for devices.
Documentation address ranges ↗09 / Networking
Remember a website address
Think of a contact list that remembers phone numbers. DNS does something similar for websites: it matches a name with a computer address. A cache is a temporarily remembered answer.
Try this Look up the name. Change its address, then look up the name again. Advance time twice and try another lookup.
Look for The remembered answer stays until its 60-second timer runs out, even after the current address changes.
- Current website address
- 192.0.2.10
- Pretend clock
- 0 seconds
- Remembered address
- Empty
- Remember for
- 0 seconds
Look up the name to remember its address for 60 pretend seconds.
The idea: A saved answer can be useful and still be out of date.
A little more detail +
Remembering an answer saves time. After its timer expires, the system asks for a fresh answer. This example uses a pretend website and clock, so no real website is contacted.
DNS concepts ↗10 / Networking
Start a conversation
Imagine saying “Hello,” hearing “Hello, I’m ready,” then replying “Ready too.” Computers use a similar three-step greeting before sending some kinds of data.
Try this Choose “Hello,” then “Hello, ready,” then “Ready too.” The short names in brackets are the computer messages.
Look for Both sides check that the other is ready before the conversation starts.
Your computer starts. Choose “Hello.”
The idea: Connecting and keeping a conversation private are two different jobs.
A little more detail +
The messages are called SYN, SYN-ACK and ACK. Together they start a TCP connection. Starting the conversation does not make it private; encryption is a separate protection.
TCP specification ↗11 / Security
Which rule comes first?
A firewall is like a gatekeeper that follows rules. This one reads from the top and stops at the first rule that fits. A “block everything” rule at the top stops every visit.
Try this Move “Allow website visits” above “Block everything.” Test a website visit, then try another kind of visit.
Look for The same rules can give a different result when you change their order.
“Block everything” is first, so every visit is stopped.
The idea: The order of instructions can matter as much as the instructions themselves.
A little more detail +
A specific rule must come before a wider rule that would catch the same visit. This is a small example of a first-match firewall; real products have additional settings and behavior.
NIST firewall guidance ↗12 / Security
Add another kind of check
A password and a PIN are both things you know. A security key is something you have. A fingerprint is something about you. Good extra checks use different kinds of proof.
Try this Choose Password and PIN. Then replace PIN with Security key. Compare the result.
Look for Two secrets you know are still the same kind of check.
Choose Password and PIN, then compare them with Password and Security key.
The idea: Another kind of proof adds something that repeating the same kind does not.
A little more detail +
Multi-factor authentication uses different kinds of proof, often shortened to MFA. Knowing a password and having a security key are different kinds. Some methods protect better than others, and fingerprints are normally part of a device-based check.
NIST authentication guidance ↗13 / Security
Spot a tricky message
Your school’s website address is school.example. This pretend email asks you to sign in. Tap the sender, the deadline, the link and the request for a password to inspect each clue.
Try this Find all four clues. Then decide how you would check the message without using its link.
Look for A message can look official while its website address and requests tell a different story.
School IT Support
Your account needs attention
Use the button below to keep your account.
Select part of the message to inspect it. Nothing opens a website or sends mail.
The idea: When a message feels urgent, pause and check through a route you already trust.
A little more detail +
Pause when a message pressures you or asks for secrets. Open a website you already trust or ask a known contact. A logo, correct spelling or an urgent deadline does not prove that a message is real.
CISA phishing guidance ↗14 / Security
Give a message a fingerprint
A computer can turn a message into a short code called a hash. Think of it as a digital fingerprint used to compare things. It is not a secret version of the message.
Try this Make the two messages identical. Then change one letter or punctuation mark and compare them again.
Look for The same message gives the same code. A tiny edit usually changes much of the code.
Use sample sentences here, not passwords or private information.
The idea: A digital fingerprint helps you notice that something changed.
A little more detail +
This example uses a method called SHA-256. A matching hash can help check a file against a trusted copy, but it does not by itself prove who made the file. Hashing is different from encryption, which can be reversed with the right key.
Secure Hash Standard ↗15 / Security
Find a copy that survives
You finish a project at 2 p.m. Now imagine the computer breaks, or harmful software locks its files. Pick the problem, then try each saved copy. A synced folder automatically follows changes to the working files.
Try this Test all three copies after each problem. Notice which ones still work and when they were saved.
Look for The newest copy is useful only if it survives. A copy on the broken computer may be lost with it.
Which copy remains usable after this incident?
The idea: A good backup must survive the problem and let you get your work back.
A little more detail +
A separate backup can survive trouble that reaches the working files. But a noon copy does not include changes made after noon. Backups need protection and regular restore checks, not just a folder with “backup” in its name.
CISA ransomware recovery guidance ↗16 / Security
What needs protecting?
Security protects three everyday things: who can see information, whether it stays correct, and whether people can use it when needed. Match each short story to the main problem.
Try this Read the story and choose the closest match. Then try the next story.
Look for A privacy problem is different from wrong information or a service that will not open.
A private student record is viewed by someone without permission.
Choose the property that best matches the scenario.
The idea: Protecting information includes keeping it private, correct and usable.
A little more detail +
The technical names are confidentiality (keep it private), integrity (keep it correct) and availability (keep it usable). One incident may affect more than one; these stories ask about the clearest problem.
NIST security objectives ↗