フラッシュ暗算

【feature】
・ 7 levels
・ From easy 1 digit to difficult 4 digit
・ Level 1 has 6 single-digit numbers, level 2 has 6 double-digit numbers, level 3 has 10 double-digit numbers, level 4 has 4 3-digit numbers, level 5 has 8 single-digit numbers, and level 6 has 1 digit. 12 digit numbers, level 7 consists of 6 4-digit numbers