Math games that let you visualize math and experiment with it. Is there any math games like Euclidea that let’s you experiment with math. Like graph theory, topology, discrete math, continuous math?
 A: Some of my favorites:

XSection -- teaches you how to construct cross sections of polyhedron (sometimes the questions get super hard)
Hexio -- puzzles with a lot of basis in graph theory
4D Maze -- as the name suggests, let you experiment with 4D space
Curved Spaces -- for students who are interested in 3D-manifolds and topology

All the games above are downloadable in the App Store, and the first three are downloadable in Google Play.
If you are interested in more games, you can check out the following website:
Topology and Geometry Software
A: My three recommendations
Rummikub: If you love numbers, then you will love Rummikub. The game includes $104$ number tiles and every player starts with $14$ number tiles. In order to win, the player must find a way to play all of their tiles. The game is popular with children and the general public.  This paper
   investigates the computational complexity of the game over various
   input parameters. 

Set: A classic card game that includes a lot of mathematics. Set has a simple goal: to find special triples called “sets” within a deck of $81$ cards. This article describes how mathematicians have solved a problem about the pattern-matching card game Set that predates the game itself. The solution lead to advances in other combinatorics problems. This paper includes a summary of the mathematics behind the game.

Chess: What does chess require? Concentration, planning, patience, self-control (playing fast does not pay off), conduct rules, mistake learning, etc. The relationship between chess and mathematics can be seen in a number of ways:


*

*Chess promotes thinking skills of higher order

*Analysis of positions has a lot in common with mathematical problems

*Correlation: to decide what piece is best to sacrifice at a certain
point

*Introduces a coordinates system

*Introduces geometric concepts (files, rows, diagonals)

*Requires constant calculation

*Develops visual memory

*Spatial reasoning skills

*Capacity to predict and anticipate consequences


This paper goes over relationships between mathematics and chess. The great courses series also has a lecture devoted to the relationship between mathematics and chess.

A: Sprouts, a game invented by John Conway. 
