FLASH SUMS
Numbers flash. You hold the total. No peeking.
Type the final total on the keypad. Streaks multiply your score.
How to play Flash Sums
Flash Sums is flash anzan: the mental-arithmetic drill from Japanese soroban training, where numbers are shown one after another and only the running total is kept. Numbers appear in the middle of the screen one at a time and vanish. Nothing is written down and nothing stays on screen: you hold the total in your head, and when the sequence ends you type what you got.
Pick a speed and an operation set, press Start, and the round runs. Type the final total on the keypad and submit it; the game tells you at once whether you were right and what the answer was.
Controls
- Keyboard: type digits directly, Backspace corrects, − flips the sign for a negative total, Enter submits and Esc pauses.
- Touch: the on-screen keypad has the same keys, including the sign toggle and the submit button.
Speeds, operations and streak scoring
Four speeds change three things at once: how many numbers flash, how many digits each has, and how long each stays on screen. Easy shows 5 single-digit numbers at 1.4 seconds each. Medium shows 10 two-digit numbers at 0.85 seconds. Hard shows 15 three-digit numbers at 0.55 seconds. Insane shows the same 15 three-digit numbers at 0.32 seconds. Roughly three a second, which is where flash anzan starts to feel like the real thing.
Operations are addition only, or mixed addition and subtraction; mixed sequences are generated so the running total never goes negative mid-way. Each correct round scores the speed’s base points multiplied by a streak bonus that grows 10% per consecutive correct answer and caps at triple, plus a bonus for answering inside par. One wrong answer resets the streak.
Questions
Is Flash Sums free?
Yes, completely. There is nothing to download, nothing to install, no account and no sign-up. The page loads and the game runs in the browser tab, on desktop or phone.
What is flash anzan?
Flash anzan is a mental-arithmetic drill from Japanese soroban (abacus) practice. A sequence of numbers is flashed on a screen one at a time, and the competitor adds them in their head as they go, reporting only the final total. Nothing is written down. Flash Sums is that exercise, with four speeds and an optional subtraction mix.
How do I get better at flash anzan?
Stay at a speed until you are consistently right rather than jumping ahead: the skill is holding and updating one number, and it collapses if you try to re-read digits you have already passed. Most people improve fastest by adding left to right (hundreds, then tens, then units) rather than the way addition is taught on paper.
Does it work on a phone?
Yes. The number pad on screen takes every input the keyboard does, including the sign toggle for negative totals, so the game plays the same on a touchscreen.
More games like this
- Number NovaArcade mental-math drills against a 60-second clock.
- Cross MathFill a 3x3 grid so every row and column reads as a true equation.
- Mind SnapA pattern of tiles flashes; tap back the ones you remember.