What is Nap'Sac?
Nap'Sac is a free puzzle and thinking game for iOS, Android and the web, based on the knapsack problem from computer science. Players choose items with a value and a weight to maximize total value without exceeding the backpack's capacity.
Is Nap'Sac free?
Yes. Nap'Sac is free to download and play on iOS and Android, with no ads and no real-money purchases.
Who is Nap'Sac for?
Nap'Sac is suitable for players age 8 and up who enjoy logic puzzles, brain training, daily competitions, or competitive multiplayer.
What game modes does Nap'Sac have?
Adventure (60+ puzzles across themed arenas), Daily Quiz (one shared puzzle per day with global leaderboard), Weekly Arena (a new themed arena each week), Time Attack (endless against the clock), ranked Battles (PvP), and asynchronous Friend Challenges.
Think you can outsmart a sentient sack?
Your backpack is hungry for treasures. Pack the most valuable items without overloading it. Solve puzzles, conquer arenas, battle friends and compete with players worldwide.
How It Works
Simple to learn, endlessly challenging. Based on the famous knapsack problem from computer science.
Meet the Items
Each item has a value and a weight. Pick the ones worth the most.
Tap to Select
Tap tiles to add items to your backpack. Watch the capacity bar fill up.
Watch Your Weight
Don't exceed your backpack's capacity. Green means go, red means stop.
Earn Stars
Find the optimal value to earn up to 3 stars. Fewer attempts means more stars.
Try It Right Now
This is a real knapsack puzzle. Select items to maximize value without exceeding the weight limit. Can you find the perfect solution?
Six Ways to Play
Whether you want a chill solo adventure, a daily ranked race, or a real-time duel with a friend, there is a mode for you.
Adventure
CampaignExplore themed arenas across 60+ puzzles. From Grasslands to Summit, each arena gets harder. Defeat bosses to unlock the next world.
Daily Quiz
DailyOne puzzle per day, same for everyone worldwide. Race against the clock, climb the global leaderboard, and keep your streak alive.
Weekly Arena
WeeklyA new themed arena every week. Reach the top and earn medals before the timer resets — only the fastest packers make the podium.
Time Attack
EndlessHow many puzzles can you solve before time runs out? A fast-paced endless mode that tests your speed and accuracy.
Battles & Challenges
VersusDuel friends and rivals on the same puzzle. Send asynchronous challenges or climb the ranked PvP ladder from Rookie to Grandmaster.
My Nap'Sac
CollectionSpend your hard-earned stars to collect adorable Nap companions, decorate your world with ponds and trees, and watch your village grow.
Why You'll Love It
Nap'Sac blends brain-teasing puzzles with a playful adventure that keeps you coming back day after day.
Train Your Brain
Based on the NP-complete knapsack problem. Every puzzle is a unique optimization challenge.
Global Competition
Same daily puzzle for everyone. Compete for the top spot on the worldwide leaderboard.
Battle Friends
Send challenges to friends, accept their duels, and climb a ranked PvP ladder.
Daily Streaks
Solve the daily quiz to build your streak. Reminders are optional and fully under your control.
Themed Arenas
Journey through Grasslands, Forge, Inferno, Crystal Caves, Summit and rotating weekly arenas.
Earn Stars & Medals
3 stars for first-try perfection, gold medals for weekly podiums. Collect them all to unlock new content.
Play Anywhere
Optional account to sync progress across devices. Play offline anytime — your scores sync when you reconnect.
11 Languages
English, French, German, Spanish, Italian, Portuguese, Dutch, Japanese, Korean, Chinese and Russian.
Meet the Characters
Your backpack has many moods. Collect them all in My Nap'Sac.
Ready to Pack?
Download Nap'Sac for free and start your puzzle adventure today. Prove you're smarter than a backpack.