Pendidikan abad 21 harus memfasilitasi pembelajaran jarak jauh dan siswa dituntut untuk memiliki kemampuan berpikir kritis dan pemecahan masalah. Oleh karena itu penting untuk mengembangkan media pembelajaran matematika berbasis teknologi dalam melatihkan kemampuan berpikir kritis dan pemecahan masalah. Jenis penelitian ini adalah penelitian pengembangan dengan pendekatan kuantitatif. Fase pengembangan terdiri dari 6 fase yaitu initiation, specification, design, production, review and evaluation, delivery and implementation. Pemilihan subjek penelitian yaitu 36 siswa kelas V, 27 siswa kelas IX, dan 30 siswa kelas XII. Instrumen penelitian yaitu lembar observasi, wawancara, angket respon, serta tes berpikir kritis dan pemecahan masalah. Analisis kevalidan dan kepraktisan media PHET yang dikembangkan dengan validitas produk dan materi media, serta analisis dari analisis angket respon siswa. Sedangkan analisis keefektifan media dengan analisis tes kemampuan berpikir kritis dan pemecahan masalah. Pengembangan Media PHET yang dikembangkan melalui tahapan: (a) Menyesuaikan dengan kurikulum 2013, memilih materi dimana kemampuan berpikir kritis dan pemecahan masalah siswa masih rendah yaitu materi pecahan, pola bilangan, dimensi tiga, serta menganalisis sejauh mana kemampuan siswa, dan membuat media PHET yang mudah dioperasikan, (b) Menyusun storyboard, (c) Memilih karakter yang sesuai dengan karakteristik siswa di setiap jenjang, warna yang dapat meningkatkan semangat belajar, dan sound effect, (d) Pembuatan media PHET dengan Unity, (e) Penilaian oleh validator bahwa media PHET dan instrumen valid dan reliabel, dan (f) Implementasi media untuk setiap jenjang didapatkan jika media PHET praktis. Penerapan media PHET terhadap siswa juga dikatakan efektif karena dapat melatihkan kemampuan berpikir kritis dengan hasil tes pada kategori sedang dan tinggi. 21st century education must facilitate distance learning, and students are required to have critical thinking and problem-solving skills. Therefore, it is important to develop technology-based mathematics learning media in practicing critical thinking and problem-solving skills. This type of research is development research with a quantitative approach. The development phase consists of 6 phases: initiation, specification, design, production, review and evaluation, delivery and implementation. The selection of research subjects were 36 students of class V, 27 students of class IX, and 30 students of class XII. The research instruments are observation sheets, interviews, response questionnaires, and critical thinking and problem-solving tests. Analysis of the validity and practicality of PHET media developed with the validities of media products and materials, as well as analysis of student response questionnaire analysis. The analysis of the effectiveness of the media with the analysis of critical thinking skills and problem solving. The development of PHET Media which was developed through the following stages: (a) Adapting to the 2013 curriculum, choosing materials where students' critical thinking and problem solving skills are still low, namely fractional material, number patterns, three dimensions, as well as analyzing the extent of students' abilities, and making PHET media that easy to operate; (b) Prepare storyboards; (c) Choose characters that match the characteristics of students at each level, colors that can increase enthusiasm for learning, and sound effects; (d) Making PHET media with Unity; (e) Assessment by the validator that PHET media and instruments are valid and reliable; (f) Implementation of media for each level is obtained if PHET media is practical. The application of PHET media to students is also said to be effective because it can train critical thinking skills with test results in the medium and high categories.