This survey book reviews four interrelated areas: (i) the relevance of heuristics in problem-solving approaches - why they are important and what research tells us about their use; (ii) the need to characterize and foster creative problem-solving approaches - what type of heuristics helps learners devise and practice creative solutions; (iii) the importance that learners formulate and pursue their own problems; and iv) the role played by the use of both multiple-purpose and ad hoc mathematical action types of technologies in problem-solving contexts - what ways of reasoning learners construct when they rely on the use of digital technologies, and how technology and technology approaches can be reconciled. This work was published by Saint Philip Street Press pursuant to a Creative Commons license permitting commercial use. All rights not granted by the work's license are retained by the author or authors.