Rafael's baby sister, Essie, is a toddling terror who doesn't understand boundaries and keeps grabbing all of his toys. So, Rafael decides to build a wall to protect his belongings. He uses shoeboxes, paper rolls, magazine holders, and other found objects. Through trial and error mixed with a grasp of 3-D geometry and spatial reasoning, Rafael builds his fortification. But is it Essie-proof? This question is answered as soon as naptime ends and Essie comes busting through the wall. The toys, however, are safe because Essie loves knocking down the wall d playing with her big brother st of all. Lacika and Martinez do a wonderful job in this Storytelling Math title of bringing a STEM topic to life, and the illustrations clearly depict Rafael's thoughts and building process. Because Rafael's family is Chicanx (Mexican American), the text smoothly incorporates Spanish vocabulary, which is defined in a glossary. The back matter also includes an "Exploring the Math'' section featuring math notes, activities, and a link to additional STEM support material.

Rafael wants to keep his toys safe from his rambunctious toddler sister, Essie. What can he do?Nothing seems to ward off the human tornado that is his little sister. Blocking the doorway with a "no pasar" sign was a bust-Essie can't read! Maybe he can protect his toys with a barricade. Commandeering an array of household items, Rafael begins constructing "un muro. A wall." Puzzle boxes, cereal boxes, packing boxes, a portable cooler, and even a roll of toilet paper are pressed into service. Building the wall is not as easy as he thought. Using spatial relations and problem-solving skills, Rafael successfully constructs an impassable and kid-proof obstacle to protect his toys-or has he? Before he knows it, the irrepressible Essie barrels through the wall, and Rafael finally realizes what his sister has been trying to do-it's not his toys she wants to play with but him. Lacika's STEM-driven story highlights early math skills, self-directed creative play, and the power of collaboration. Using simple declarative sentences with a peppering of Spanish vocabulary, the text unfolds Rafael's dilemma organically. The bright, full-color digital illustrations show various adults going about their daily routines oblivious to the churning sibling undercurrents in their Chicanx middle-class household. A Spanish glossary and math activities are included. (This book was reviewed digitally.)A fun look at spatial and sibling relationships. (Picture book. 4-7)