# Desmos Marbleslides

This week, Desmos released a new activity called Marbleslides. As you might have heard (or seen), it’s delightful:

Dan Meyer wrote about the activity on his blog, and our resident wordsmith dropped a marbleslides post on the official Desmos blog.

[Psst: If you haven’t played yet, and want to… Go here.]

In reflecting on what I love about marbleslides, my thoughts go back to the session Katie Reneau and I co-presented at this year’s CMC North and South conferences. We presented four principles that we’ve found effective in task selection and implementation with our own students.

1. Use tasks that build capacity for SMP 3.
2. Use tasks that are accessible and extendible.
3. Use tasks that encourage iteration.
4. Use tasks that have room for multiple approaches.

There’s not much in the way of SMP 3 (constructing viable arguments…), but marbleslides is an absolute gold mine when it comes to the other three principles.

#### Accessible and Extendible

The activity kicks off with a challenge that “even your baby cousin” could tackle. Provided he or she is willing to hit the “launch” button.

From there, the challenges grow. Marbleslides adds one layer at a time, providing students with digital sandboxes in which to explore constants and coefficients, translations and dilations, concavity and restrictions.

As students build their skills, Marbleslides pulls back the supports. Students are asked to find (and reflect on) solutions to increasingly complex challenges.

#### Iteration

In our conference session, Katie and I used an Open Middle problem to illustrate the meaning (and value) of iteration in math tasks. We both love problems that offer students some early reward, and them immediately invite them to dig deeper, work smarter, etc.

For Marbleslides, imagine this sequence:

• A student builds a solution, clicks launch. No stars. (Bummer.)
• But she tries again. And gets a star. (:internal-fist-pump:)
• She adjusts her graph (or graphs), and gets two more stars. (Nice!)
• So close… Just one more… A few more tweaks (and attempts), and she’s like:

• But then a classmate throws down a challenge: Five parabolas? Betchacant with just three.
• And the tweaking, the improving—the iterating—continues.

#### Multiple Approaches

Something else I love about marbleslides? Students can legitimately take alternate paths to the solution. Years ago I began asking students (almost like a broken record), “Great! Can you solve it another way?”

For the record, this prompting works out much better when there’s more than one mathematically meaningful approach.

And on most marbleslides levels (especially later in the activities), I’m pretty sure there are. From different paths, to different functions, to minimizing equations, to minimizing the time it takes to get all four stars… There are a lot of options for pressing deeper on any part of these tasks.

#### Invitation

If you haven’t tried out marbleslides yet, pick your flavor (lines, parabolas, exponentials, rationals, periodics), and let me know what you think.

If you’re already tried it, do me a favor: Save a GIF of your favorite solution (yours, a colleague’s, or a student’s) and drop it in the comments.