How to Play FibDefense
Tower defense reimagined around mathematics. Every shot, every kill, every strategy is governed by the Fibonacci sequence.
The Exact-Kill Rule
A tower fires when a monster's remaining HP is greater than the tower's damage — meaning it can only contribute without overkilling. Chain your Fibonacci towers so their shots sum precisely to each enemy's HP, leaving nothing left over.
See It In Action
A tower fires when the monster's remaining HP is greater than the tower's damage — it won't fire if it would overkill. Your job is building the right sequence so HP reaches exactly zero.
✅ Good sequence — HP: 8
❌ Wrong tower — HP: 8
✅ Good sequence — HP: 13
The Eight Tower Tiers
Each tier deals exactly its Fibonacci number in damage. Names below are from the Fantasy theme — every theme has its own tower designs.
A live board — place your Fibonacci towers along the path so the right creeps walk into range and drain to exactly zero.
The Fibonacci Engine
Every tower deals a Fibonacci number of damage — 1, 2, 3, 5, 8, 13, 21, 34 — and never overkills. To defeat an enemy, your towers' hits have to add up to its exact HP.
The Fibonacci numbers form a complete sequence — every whole number is reachable as a sum of them — and because your smallest tower deals exactly 1 damage, every enemy's HP is always solvable. Usually there are many ways to do it, and the toughest enemies need repeated hits from your strongest towers, so the real puzzle is finding an efficient solution.
Worked Examples
One tidy way to hit each total — in-game you can reach the same HP other ways too.
Game Modes
Three modes, each demanding a different Fibonacci strategy.
Classic
20 hand-crafted waves. Campaign ends when you beat wave 20 or run out of lives.
Boss appears every 10th wave — 3× HP, 0.8× speed.
Continuous
No wave boundaries. Monsters spawn non-stop and grow stronger over time.
Every 100 kills triggers a boss: ~5–9× current creep HP, 0.6× speed, 10× gold.
Endless
Waves continue past wave 20, procedurally generated forever.
Boss appears every 10th wave — 3× HP, 0.8× speed.
Boss Encounters
Bosses have massive HP that requires long Fibonacci chains across your full path. How they appear depends on your mode.
Appears at every 10th wave. Boss has 3× the HP of that wave's creeps and moves at 0.8× speed.
Triggered every 100 kills. Boss has ~5–9× current creep HP at 0.6× speed — and pays 10× gold.
Boss HP is always a valid Fibonacci sum — there's always a solution, but finding it under pressure is the challenge.
Difficulty Levels
Choose your challenge. Relaxed and Normal are free — unlock premium for Hard and Expert.
Strategy Tips
Plan your path layout before placing towers. Once a tower is down, rearranging costs resources.
Think of each enemy's HP as a Fibonacci sum to solve. Write it out if you need to.
Higher-tier towers don't replace lower ones — you need both. A Tier-8 tower (34 dmg) can't handle a HP:3 enemy.
Long-press a placed tower to sell it for 60% back. Rearranging costs gold, but it's better than a monster escaping.
You earn bonus gold at the end of each wave — save it for higher-tier towers as HP values climb.
Bosses require full-path coverage. Make sure every Fibonacci tier is represented somewhere on the route.
Ready to Test Your Math?
Download FibDefense and start with Relaxed mode — free forever.