This is a great digital manipulative to help students explore definitions and properties interactively.

This has the potential to be an absolutely wonderful tool. It is not there yet. The website is an interactive geometry text book. Originally designed for high school, it is easily used in lower grades to introduce a wide variety of topics. You have to be careful to avoid the ads that look like they are part of the site. There can be a lot of them. I also got one about how to improve your abs. While possibly helpful in its own way, not helpful during a classroom introduction on angles. The great part is that for a topic, you will get an interactive model, key vocabulary with definitions, demonstrations, possible extension ideas, and related topics. The interactive models, in my opinion, are the biggest asset of this website. They will give students visual models of the topics that they can move around and see how the vocabulary is related. For example, when introducing angles, the model lets you move around the angle and will give you the exact measurement as well as the type of angle (acute, obtuse, right...) as you move it. If they can get rid of the ads, or make them more appropriate, this could be a wonderful teaching tool that would be available to the students anywhere that they can get online.

This website has an excellent section dedicated to geometric constructions. The number of constructions is just as impressive as the quality found in each one. You can find every construction mentioned in the Common Core State Standards for geometry, in addition to many more for your advanced learners. Each construction includes a step-by-step animated demonstration of the construction, a list of the steps for offline use, and a formal proof of the construction. And this is just the beginning. There is also a page on the site dedicated to the Common Core State Standards that hyperlinks each standard to related content. The creator is very active and always adding more valuable content. I like the comprehensive coverage of the geometry curriculum on this site and the dynamic, interactive animations that illuminate otherwise abstract mathematical concepts. There are ads on the site (mostly educational), so be aware of this as your students access the content. One additional comment: the site has been updated to be compatible with the iPad! This is exciting for me, since my students are using iPads.