孩子用直式從個位算起，每一位自己轉出答案。加法個位滿十時，要把接力棒（1 個十）交給十位，就是進位；減法上面不夠減時，要向十位借 1 根接力棒，十位少 1、個位多 10，就是退位。第三關的接力棒會一路傳到百位；第四關是三位數的加減直式，還有十位是 0 時要先向百位借的題目（例如 703 − 268）。
適合年級：二年級（約 7～8 歲）。對應 108 課綱（十二年國教）數學單元：二年級「二位數加法（進位）」、「二位數減法（借位）」和「三位數加減直式（進位、退位）」。各版本教科書的單元順序不同，完整對照請看國小數學課綱對照表。免費、無廣告、不用註冊，手機、平板、電腦打開就能玩，題目有注音，也會念出算式。
陪玩小提醒：常見的錯誤是忘了進位、把減法倒過來算（3 − 8 算成 8 − 3），或借完以後忘了十位要少 1。遊戲會指出是哪一種，請孩子說說看接力棒是從哪裡交到哪裡。
Children work column sums from the ones, turning a dial for each digit. When the ones reach ten, they hand the relay baton (one ten) to the tens: that is carrying. When the top digit is too small, they borrow a baton from the tens: the tens go down by one and the ones go up by ten. In level 3 the baton travels all the way to the hundreds, and level 4 is three-digit column sums, including borrowing across a zero (703 − 268).
Suits Grade 2 (about age 7–8) in Taiwan. Taiwan curriculum (12-year basic education) units: Two-digit addition with carrying, Two-digit subtraction with borrowing, Three-digit column adding and subtracting (Grade 2). Free with no ads and no sign-up, in Traditional Chinese with zhuyin and in English, with questions read aloud. See the Taiwan elementary maths curriculum map.