Here's a zombie themed set of puzzles for working on addition facts with sums to 20.
FREE Plants vs. Zombies Themed Printable Games (Sneak in a little learning with a theme they love!)
Math Games Math Vs Zombies by Tap To Learn ($0.00) ✔ 3 detailed, extremely fun to play worlds with 8 levels each. ✔ Questions support addition, subtraction and multiplication problems. ✔ Complete Open Feint integration with over 15 achievements. ✔ Global leader boards for each level. ★ SYLLABUS COVERED ★ ‣ Addition ‣ Subtraction ‣ Multiplication