The Arena Games of Knowledge

Games you win by writing code, in Python or JavaScript: races, duels, survival and team games, and open challenges judged by hidden trials. Choose one from the menu.

Every game pays experience and has its own board in the Hall of Adepts.

Members only

Playing in the Arena is part of Learn, included with the Reader and Downloader memberships. Anyone may watch the matches.

See memberships

The games and challenges

Race and sprint · new in the Arena

Incantation Sprint

Tiny puzzles drop one after another (reverse every word, sum the runes, read the old numerals) and the first passing solve(x) scores. The ones you leave pile up, faster as the match goes on, and eight waiting puts you out. Every kind of puzzle names a lesson that teaches it.

See Incantation Sprint
Players
2 to 8, head to head or a crowd
A match
6, 9 or 12 minutes
You write
solve(x), fresh for each puzzle
Against
other players, or Xher's bots

Against the clock, and against each other. Every game takes Python or JavaScript.

Race and sprint

Dragon Racing

A racetrack seen from above. Your steer(sensors) flies a dragon with momentum and drift round a thirty-second lap; race the ghosts of the best laps, and Xher's dragons for bronze, silver, gold and Xher's own time. One more try is always a click away.

See Dragon Racing
Players
you, against the clock
A lap
about thirty seconds, on three tracks
You write
steer(sensors)
Against
the ghosts of the best laps, and Xher's medal times

Against the clock, and against each other. Every game takes Python or JavaScript.

Survival under pressure

The Transmutation Line

Orders pour down an alchemist's line, faster and longer, and the manual gains a new operation every 45 seconds. Write each into your spell before a wrong product breaks your vessels.

See The Transmutation Line
Players
one against one
A match
3, 5 or 8 minutes
You write
transmute(order)
Against
another player, or one of Xher's bots

One against one: the pressure rises until one of you breaks. Every game takes Python or JavaScript.

Survival under pressure

Storm of Stars

Steer a star-ship through a storm that thickens by the minute, as swift stars, drifters, comets, splitters and seekers join it. Teach your ship each one while it flies, and catch stardust as you go.

See Storm of Stars
Players
one against one
A match
3, 5 or 8 minutes
You write
move(view)
Against
another player, or one of Xher's bots

One against one: the pressure rises until one of you breaks. Every game takes Python or JavaScript.

Live-coded duels

The Spell Duel

Mages trade fire, frost and storm, round after round, while you rewrite your mage's spell mid-duel. Read your foes' habits, ward what is coming, and fell them for the bout.

See The Spell Duel
Players
one against one up to five against five
A match
3, 5 or 8 minutes
You write
cast(view)
Against
other players, or Xher's bots

Rewrite your spell while the duel runs. Every game takes Python or JavaScript.

Live-coded duels

Ward and Breach

A new Law every two minutes says which sigils are genuine. Write a ward that judges them truly, and breaches that slip past your rivals' wards; patch your ward whenever something gets through.

See Ward and Breach
Players
one against one up to five against five
A match
three, five or seven Laws
You write
ward(sigil) and breach(view)
Against
other players, or Xher's bots

Rewrite your spell while the duel runs. Every game takes Python or JavaScript.

Team games · new in the Arena

The Familiar Swarm

Twenty familiars, one function to move them all. Gather moonstones on an open field while the other side's swarm does the same; flock, scatter and guard, and a three-line change can turn the match around.

See The Familiar Swarm
Players
one against one up to three against three
A match
3, 5 or 8 minutes
You write
move(me), for each familiar
Against
other players, or Xher's bots

Sides of many, in mazes and on open fields. Every game takes Python or JavaScript.

Team games

Find & Destroy

Hunt a dark maze for talismans, carry them home, and fight rival explorers for them with wards and dispels. Crests for life, barriers at home.

See Find & Destroy
Players
one to twenty-five a side
A match
20 minutes to two hours
You write
explore(view), ward(view) and dispel(view)
Against
other players, or Xher's bots

Sides of many, in mazes and on open fields. Every game takes Python or JavaScript.

Team games

Tower

Teams race through a maze to three towers, claim them, and hold them against all comers with wards and dispels written in Python or JavaScript.

See Tower
Players
one to twenty-five a side
A match
20 minutes to two hours
You write
explore(view), ward(view) and dispel(view)
Against
other players, or Xher's bots

Sides of many, in mazes and on open fields. Every game takes Python or JavaScript.

Team games

Capture the Flag

Teams write explorers in Python or JavaScript and race them through a dark maze to the flag, in bot races and live rounds, from Small mazes to Vast.

See Capture the Flag
Players
one to twelve a side
A round
a race through a maze, Small to Vast
You write
explore(view)
Against
other teams, or Xher's bots

Sides of many, in mazes and on open fields. Every game takes Python or JavaScript.

Challenges · 100 XP each

Novice

First trials: strings, lists, loops and counting, each with a catch or two in the hidden trials. The examples are shown; the trials that judge you are hidden, and only a spell that survives them all is sealed. Every challenge takes Python or JavaScript, and a second language pays half again, without points.

  1. 1
    The Mirror Sigil Strings and palindromes · solved by 0 adepts
    Python JavaScript
  2. 2
    The Tally of Runes Counting with a dictionary · solved by 0 adepts
    Python JavaScript
  3. 3
    The Balanced Wards Stacks · solved by 0 adepts
    Python JavaScript
  4. 4
    The Roman Year Numbers and greedy choices · solved by 0 adepts
    Python JavaScript
  5. 5
    The Shifted Scroll Characters and wrapping arithmetic · solved by 0 adepts
    Python JavaScript
  6. 6
    The Litany of Runs Run-length encoding · solved by 0 adepts
    Python JavaScript
  7. 7
    The Missing Page Sums and sets · solved by 0 adepts
    Python JavaScript
  8. 8
    The Second Star Finding maxima in one pass · solved by 0 adepts
    Python JavaScript
  9. 9
    The Familiars' Roll Loops and divisibility · solved by 0 adepts
    Python JavaScript
  10. 10
    The Hidden Acrostic Splitting text into lines · solved by 0 adepts
    Python JavaScript
  11. 11
    The Pyramid of Stones Counting with a loop · solved by 0 adepts
    Python JavaScript
  12. 12
    The Numerologist's Root Digits and repetition · solved by 0 adepts
    Python JavaScript
  13. 13
    The Twin Ledgers Sets for fast membership · solved by 0 adepts
    Python JavaScript
  14. 14
    The Zodiac Wheel Slicing and remainders · solved by 0 adepts
    Python JavaScript
  15. 15
    The Titled Tome Words and capital letters · solved by 0 adepts
    Python JavaScript
  16. 16
    The Leap Almanac Conditions and counting · solved by 0 adepts
    Python JavaScript
  17. 17
    The Even Scales Running sums · solved by 0 adepts
    Python JavaScript
  18. 18
    The Serpent of Collatz While loops · solved by 0 adepts
    Python JavaScript
  19. 19
    The Longest Chant Tracking the best so far · solved by 0 adepts
    Python JavaScript
  20. 20
    The Hidden Word Two pointers · solved by 0 adepts
    Python JavaScript
Challenges · 250 XP each

Adept

Problems that want the right idea: stacks, sliding windows, hash maps, grids and first dynamic programming. The examples are shown; the trials that judge you are hidden, and only a spell that survives them all is sealed. Every challenge takes Python or JavaScript, and a second language pays half again, without points.

  1. 21
    Kindred Incantations Grouping by a key · solved by 0 adepts
    Python JavaScript
  2. 22
    The Common Incipit Comparing strings · solved by 0 adepts
    Python JavaScript
  3. 23
    The Reading-Room Ledger Sorting and merging intervals · solved by 0 adepts
    Python JavaScript
  4. 24
    Paths Through the Stacks Counting paths in a grid · solved by 0 adepts
    Python JavaScript
  5. 25
    The Spiral Grimoire Walking a grid in a spiral · solved by 0 adepts
    Python JavaScript
  6. 26
    The Unrepeated Chant Sliding windows · solved by 0 adepts
    Python JavaScript
  7. 27
    Two Reagents to the Weight Hash maps for pairs · solved by 0 adepts
    Python JavaScript
  8. 28
    The Sieve of Eratosthenes Sieving primes · solved by 0 adepts
    Python JavaScript
  9. 29
    The Reversed Rite Stacks and postfix notation · solved by 0 adepts
    Python JavaScript
  10. 30
    The Islands of the Chart Flood fill · solved by 0 adepts
    Python JavaScript
  11. 31
    The Nine Seals Checking rows, columns and boxes · solved by 0 adepts
    Python JavaScript
  12. 32
    The Fewest Coins Dynamic programming · solved by 0 adepts
    Python JavaScript
  13. 33
    The Gathered Catalogues Merging sorted lists · solved by 0 adepts
    Python JavaScript
  14. 34
    The Next Arrangement Permutations in order · solved by 0 adepts
    Python JavaScript
  15. 35
    The Richest Vein Kadane's maximum subarray · solved by 0 adepts
    Python JavaScript
  16. 36
    The Hours Between Sorting times on a circle · solved by 0 adepts
    Python JavaScript
  17. 37
    The Decoded Ways Counting with dynamic programming · solved by 0 adepts
    Python JavaScript
  18. 38
    The Oracle's Bulls Counting matches · solved by 0 adepts
    Python JavaScript
  19. 39
    The Most Spoken Names Counting and sorting by a key · solved by 0 adepts
    Python JavaScript
  20. 40
    The Zigzag Scroll Index patterns · solved by 0 adepts
    Python JavaScript
Challenges · 500 XP each

Master

Graphs, heaps, union-find, backtracking and dynamic programming, with hidden trials large enough that only an efficient spell survives. The examples are shown; the trials that judge you are hidden, and only a spell that survives them all is sealed. Every challenge takes Python or JavaScript, and a second language pays half again, without points.

  1. 41
    The Labyrinth Under the Archive Breadth-first search · solved by 0 adepts
    Python JavaScript
  2. 42
    The Reagent Satchel Dynamic programming · solved by 0 adepts
    Python JavaScript
  3. 43
    The Order of the Rites Topological ordering · solved by 0 adepts
    Python JavaScript
  4. 44
    The Faithful Copy Edit distance · solved by 0 adepts
    Python JavaScript
  5. 45
    The Shortest Pilgrimage Dijkstra's shortest paths · solved by 0 adepts
    Python JavaScript
  6. 46
    The Longest Rising Omen Longest increasing subsequence · solved by 0 adepts
    Python JavaScript
  7. 47
    The Arithmetic of the Magi Parsing expressions · solved by 0 adepts
    Python JavaScript
  8. 48
    The Wildcard Ward Pattern matching with dynamic programming · solved by 0 adepts
    Python JavaScript
  9. 49
    The Ley Lines Minimum spanning trees · solved by 0 adepts
    Python JavaScript
  10. 50
    The Gathered Covens Union-find · solved by 0 adepts
    Python JavaScript
  11. 51
    The Longest Palindrome Expanding around centres · solved by 0 adepts
    Python JavaScript
  12. 52
    The Queens of the Board Backtracking · solved by 0 adepts
    Python JavaScript
  13. 53
    The Cisterns of the Roof Two pointers · solved by 0 adepts
    Python JavaScript
  14. 54
    The Largest Hall Monotonic stacks · solved by 0 adepts
    Python JavaScript
  15. 55
    The Running Median Two heaps · solved by 0 adepts
    Python JavaScript
  16. 56
    The Watchtower Window Monotonic deques · solved by 0 adepts
    Python JavaScript
  17. 57
    The Tour of the Sanctums Dynamic programming over subsets · solved by 0 adepts
    Python JavaScript
  18. 58
    The Kth Arrangement Counting with factorials · solved by 0 adepts
    Python JavaScript
  19. 59
    The Priestess's Calendar Weighted interval scheduling · solved by 0 adepts
    Python JavaScript
  20. 60
    The Path of Greatest Ascent Ordering a grid for dynamic programming · solved by 0 adepts
    Python JavaScript
Challenges · 1,000 XP each

Ipsissimus

The hardest of all, for the utmost mastery of the language: automata, bridges and flows, an interpreter, suffix machines and the cleverest data structures. The trials are vast and merciless. The examples are shown; the trials that judge you are hidden, and only a spell that survives them all is sealed. Every challenge takes Python or JavaScript, and a second language pays half again, without points.

  1. 61
    The Regular Incantation Matching patterns with an automaton · solved by 0 adepts
    Python JavaScript
  2. 62
    The Bridges of the Ley Network Finding bridges in a graph · solved by 0 adepts
    Python JavaScript
  3. 63
    The Distinct Passages Suffix automata · solved by 0 adepts
    Python JavaScript
  4. 64
    The Lisp of the Lost Order Interpreting a language with scopes · solved by 0 adepts
    Python JavaScript
  5. 65
    The Least Window Sliding windows with counts · solved by 0 adepts
    Python JavaScript
  6. 66
    The Greatest Flow Maximum flow · solved by 0 adepts
    Python JavaScript
  7. 67
    The Sealed Square Backtracking with constraint propagation · solved by 0 adepts
    Python JavaScript
  8. 68
    The Bursting Spheres Interval dynamic programming · solved by 0 adepts
    Python JavaScript
  9. 69
    The Living Ledger Fenwick trees · solved by 0 adepts
    Python JavaScript
  10. 70
    The Skyline of the Citadel Sweep lines with a heap · solved by 0 adepts
    Python JavaScript
  11. 71
    The Memory of the Familiar Designing an LRU cache · solved by 0 adepts
    Python JavaScript
  12. 72
    The Keys of the Sealed Vault Breadth-first search over states · solved by 0 adepts
    Python JavaScript