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. A fun look at spatial and sibling relationships. -- Kirkus Reviews.