← Home
Free Game — No Login Required

Teacher's Guide: Number Ninja

Number Ninja challenges students to sort numbered blocks into order, building stairs for the ninja to travel. The visual staircase metaphor makes number sequencing concrete — students see that numbers "go up" just like stairs do. Students build the staircase one step at a time: the next step glows, and a single tap on a block drops it there. Instructions appear on level 1 and level 11 only — the two levels that introduce a mission type — so the rest of the game stays uncluttered and students read the scene rather than a caption. Because the steps fill left to right, students have to decide what comes next rather than filling in the easy ends first — and nothing is marked right or wrong until they press Play. There are two mission types: Climb missions (levels 1–10) ask for ascending order to reach the rooftop flag, and Rescue missions (levels 11–16) flip the task — students sort biggest to smallest so the ninja can descend from a tower to free a trapped friend. From level 17 on, the two missions alternate at random and the numbers widen to 1–20, so students can never sort on autopilot.

What Students Practice

  • Counting and number sequence — what comes before and after a number
  • Ordering numbers in ascending sequence (Climb missions)
  • Counting backward and ordering from greatest to least (Rescue missions)
  • Number line concepts — each step is one more, or one less, than the last
  • Switching flexibly between forward and backward order on demand
  • Deciding what comes next without seeing the finished sequence — steps are built one at a time, in order
  • Quick number comparison across a set of values

Standards Alignment

  • CCSS.MATH.K.CC.A.1 — Count to 100 by ones and tens
  • CCSS.MATH.K.CC.A.2 — Count forward beginning from a given number
  • CCSS.MATH.1.NBT.A.1 — Count to 120 starting from any number
  • CCSS.MATH.1.OA.C.5 — Relate counting to addition and subtraction (counting on and counting back)
  • CCSS.MATH.1.NBT.B.3 — Compare two numbers and record the result with >, =, and <

Classroom Tips

  • Use before formal number line instruction — the staircase metaphor primes students for the number line concept
  • Ask students to explain their sorting decisions aloud: "this block goes here because it's smaller than..."
  • Works well projected on the board as a whole-class activity — students discuss which block goes where
  • Great for differentiation: kindergarteners play early levels, second graders push past level 17 where the blocks reach 20
  • Use the Rescue levels when students are learning to count backward — the descending staircase gives them a picture for subtraction and for counting down from a number
  • Add ?level=11 to the page address to send students straight to the Rescue missions without replaying the Climb levels
  • One tap per block, so young students are not fighting a drag gesture on a tablet
  • Nothing turns red mid-puzzle — the ninja’s run is the answer check, which keeps students predicting instead of guessing-and-checking
  • If a student needs the instructions again, send them to ?level=1 (Climb) or ?level=11 (Rescue) — those are the only two levels that show them
What is the difference between a Climb mission and a Rescue mission?

Climb missions (levels 1–10) ask students to sort blocks smallest to biggest so the staircase rises to a rooftop flag. Rescue missions (levels 11–16) reverse it: the ninja starts on top of a tower and the blocks must run biggest to smallest so the stairs go down to a caged ninja on the ground. From level 17 on, each new level randomly picks one of the two, so students have to check the mission name in the header — and read the scene — before they start sorting.

What number ranges does the game cover?

Levels 1–10 (Climb) use blocks from 1 to 10, with three to six blocks per puzzle. Levels 11–16 (Rescue) use blocks from 1 to 8. From level 17 on, blocks come from the full 1–20 range, so students order teen numbers too — the staircase rescales automatically so a 20-block still fits on screen.

Can students place a block in the wrong spot?

Yes, and that is deliberate. Blocks fill the steps in order and the game does not judge a placement as it happens — students commit to a whole staircase and then press Play to watch the ninja run it. A wrong step drops the ninja and the correct order is shown, so the mistake is visible rather than silently prevented. Tapping the most recently placed block takes it back, and Reset clears the whole staircase.

How long does a session take?

Each sorting puzzle takes 1–3 minutes depending on the level. Sessions of 5–10 minutes allow students to complete multiple rounds — a good fit for a center activity or daily warm-up.

Does this work for kindergarteners?

Yes. The early levels are designed for students just learning to count and identify number order. The simple drag-and-drop mechanic is accessible for young learners on tablets.