Abacus - An electronic abacus that can be used to do arithmetic.

Circle 0 - A puzzle involving adding positive and negative integers to sum to zero.

Circle 21 - A puzzle involving adding positive and negative integers to sum to twenty one.

Circle 3 - A puzzle involving adding positive real numbers to sum to three.

Circle 99 - A puzzle involving adding positive and negative integers to sum to ninety nine.

Conway's Game of Life - Discover the rules that determine change in these simulations.

Counting All Pairs - Create a path that sets up a one-to-one correspondence between the counting numbers and infinite sets of ordered pairs of integers.

Diffy - Solve an interesting puzzle involving the differences of given numbers.

Dueling Calculators - Visualize a dramatic simulation of the effect of propagating rounding errors.

Fibonacci Sequence - Explore the Fibonacci sequence and the golden ratio.

Fractions - Adding - Illustrates what it means to find a common denominator and combine.

Fractions - Equivalent - Illustrates relationships between equivalent fractions.

Function Machine - Explore the concept of functions by putting values into this machine and observing its output.

Golden Rectangle - Illustrates iterations of the Golden Section.

Grapher - A tool for graphing and exploring functions.

Mastermind - Use inference and logic to play a game and guess a hidden pattern of pegs.

Number Puzzles - Solve puzzles involving arranging numbers on a diagram so that they add up to a given value.

Pascal's Triangle - Explore patterns created by selecting elements of Pascal's triangle.

Peg Puzzle - Win this game by moving the pegs on the left past the pegs on the right.

Percentages - Discover relationships between fractions, percents, and decimals.

Rational Numbers Triangle - Explore a triangular array that contains every positive rational number exactly once.

Sieve of Eratosthenes - Relate number patterns with visual patterns.

Tight Weave - Visualize the creation of the Sierpinski Carpet, an iterative geometric pattern that resembles a woven mat.

Turtle Geometry - Explore numbers, shapes, and logic by programming a turtle to move.

Venn Diagrams - Investigate common features of sets.