Add Game Demo: nu-niversal paperclips (#1108)

Inspired by @kiil, this PR adds another game for exploration &
inspiration - this time, based on the seminal incremental idle game
[Universal
Paperclips](https://www.decisionproblem.com/paperclips/index2.html).

This game implements a screen drawing loop with a roughly 60FPS
framerate, asynchronous user interaction via the new `job send` and `job
recv` commands, rudimentary deltatime calculations, and the ability to
save and load state memory.

The game does not feature any of the special mechanics that emerge from
the original, though a future project may emerge to make a more 1:1
replica of the original.

I have also updated the .gitignore to make sure no one accidentally
pushes their game save to the repo after trying it out. 😃

.gitignore

@@ -3,6 +3,8 @@
 # ignore the git mailmap file
 .mailmap
 
+# nu-specific
 check-files.nu
+gamestate.nuon
 
 .vscode/

games/paperclips/game.nu

@@ -0,0 +1,266 @@
+# nu-niversal paperclips - a (somewhat) faithful clone of Universal Paperclips
+# play the original at: https://www.decisionproblem.com/paperclips/index2.html
+
+# NOTE: scalars are off cuz i'm counting by pennies instead of dollars and cents
+
+const carriage_return = "\n\r"
+
+# Resets cursor to home position and hides it to prevent visual distraction
+def reset-cursor [] {
+  print -n "\e[H"  # Move cursor to home position (top-left)
+  print -n "\e[?25l"  # Hide cursor
+}
+
+# Clears all content from cursor position to end of screen
+def clear-to-end [] {
+  print -n "\e[J"  # Clear from cursor to end of screen
+}
+
+# Updates the terminal display with current game state
+def refresh-game-view [state] {
+  reset-cursor
+  render-game-display $state
+}
+
+def make-paperclip [state, amount: int] {
+  mut new_state = $state
+  $new_state.paperclips.total += $amount
+  $new_state.paperclips.stock += $amount
+  $new_state.wire.length -= $amount
+  $new_state.paperclips.current_second_clips += $amount  # Add this line
+  $new_state
+}
+
+def sell-paperclips [state] {
+  if $state.paperclips.stock == 0 { return $state }
+  # numbers picked by the OG, i haven't sussed out exactly why.
+  if (random float 0.0..1.0) > ($state.market.demand / 100) { return $state }
+  mut amount = 0.7 * ($state.market.demand ** 1.15) | math floor
+  if $amount > $state.paperclips.stock { $amount = $state.paperclips.stock }
+  mut new_state = $state
+  let transaction = $amount * $state.paperclips.price
+  $new_state.money += $transaction
+  $new_state.paperclips.stock -= $amount
+  $new_state
+}
+
+def update-demand [state] {
+  let marketing = 1.1 ** ($state.market.level - 1)
+  mut new_state = $state
+  $new_state.market.demand = ((.8 / $state.paperclips.price) * $marketing) * 1000
+  $new_state
+}
+
+def get-user-input [] {
+  let key = (input listen --types [key])
+  if ($key.code == 'c') and ($key.modifiers == ['keymodifiers(control)']) {
+    print -n "\e[?25h"  # Show cursor before exiting
+    exit
+  }
+  $key.code | job send 0
+}
+
+def format-text [prefix: string, value: number, --money --round] {
+  mut value = $value
+  if $money {
+    $value = $value / 100.0 | math round --precision 2
+  }
+  if $round {
+    $value = $value | math round --precision 2
+  }
+  # e.g. "Paperclips: XXX\n\r" or "Unsold Inventory: $X.XX\n\r"
+  $"($prefix): (if $money { "$" } else { })($value | into string --group-digits)(if $round { "%" } else { })($carriage_return)"
+}
+
+# Prints text after clearing the current line with ANSI escape code
+def clear-line [text] {
+  print -n $"\e[2K($text)"
+}
+
+def render-game-display [state] {
+  # Game title and stats
+  clear-line (format-text "Paperclips" $state.paperclips.total)
+  clear-line $carriage_return
+
+  # Business section
+  clear-line "Business:\n\r"
+  clear-line "---------------\n\r"
+  clear-line (format-text 'Available Funds' $state.money --money)
+  clear-line (format-text 'Unsold Inventory' $state.paperclips.stock)
+  clear-line (format-text 'Price Per Clip' $state.paperclips.price --money)
+  clear-line (format-text 'Public Demand' $state.market.demand --round)
+  clear-line $carriage_return
+  clear-line (format-text 'Marketing Level' $state.market.level)
+  clear-line (format-text 'Marketing cost' $state.market.cost --money)
+  clear-line $carriage_return
+
+  # Manufacturing section
+  clear-line "Manufacturing:\n\r"
+  clear-line "---------------\n\r"
+  clear-line (format-text 'Clips per Second' $state.paperclips.rate)
+  clear-line $carriage_return
+
+  # Wire section
+  if $state.wire.length == 1 { "inch" } else { "inches" }
+  clear-line $"Wire: ($state.wire.length | into string -g) (
+    if $state.wire.length == 1 { "inch" } else { "inches" }
+  )\n\r"
+  clear-line (format-text 'Wire cost' $state.wire.cost --money)
+  clear-line $carriage_return
+
+  # Autoclippers (conditional)
+  if $state.autoclippers.unlocked {
+    clear-line (format-text "Autoclippers" $state.autoclippers.count)
+    clear-line (format-text 'Autoclipper cost' $state.autoclippers.cost --money)
+    clear-line $carriage_return
+  }
+
+  # Controls
+  clear-line $"($state.control_line)\n\r"
+
+  # Clean up any trailing content from previous longer displays
+  clear-to-end
+}
+
+def main [] {
+  reset-cursor
+  print "Welcome to nu-niversal paperclips!"
+  clear-to-end
+  sleep 2sec
+  reset-cursor
+  let table_name = "clip_message_queue"
+
+  mut state = {
+    delta_time: 0sec
+    paperclips: {
+      total: 0
+      stock: 0
+      price: 25
+      rate: 0  # Changed from -1 to 0: This will show last second's rate
+      current_second_clips: 0  # Add: Accumulator for current second
+    }
+    last_second_timestamp: (date now)  # Add: Track when current second started
+    market: {
+      demand: 0
+      level: 1
+      cost: 10000
+    }
+    money: 0
+    control_line: "controls: [a]dd paperclip; buy [w]ire; price [u]p; price [d]own; [q]uit"
+    wire: {
+      length: 1000
+      cost: 2000
+    }
+    autoclippers: {
+      count: 0
+      unlocked: false
+      cost: 1000
+      multiplier: 1.25
+    }
+  }
+  let save_exists = ('./gamestate.nuon' | path exists)
+  if $save_exists {
+    $state = open './gamestate.nuon'
+  }
+  # initial setup
+  $state = update-demand $state
+  refresh-game-view $state
+  get-user-input
+
+  loop {
+    let seconds = $state.delta_time
+    if ($seconds) > (1sec) {
+      $state.delta_time -= $seconds
+      # TODO: tweak numbers
+      if (random bool --bias 0.5) {
+        let deviation = (0.75 + (random float 0.0..0.50))
+        $state.wire.cost *= $deviation
+        if $state.wire.cost < 1200 {
+          $state.wire.cost = 1200
+        } else if $state.wire.cost > 3000 {
+          $state.wire.cost = 3000
+        }
+      }
+      $state = update-demand $state
+
+      # Calculate total autoclipper production for this time period
+      let amount = (($seconds | into int | $in / 1000000000) * $state.autoclippers.count) | math round
+      mut index = 0
+      while $index < $amount {
+        $state = make-paperclip $state 1
+        $index += 1
+      }
+
+      $state = sell-paperclips $state
+    }
+    let prev = date now
+
+    # Check if a second has passed and roll over counters
+    let now = date now
+    if ($now - $state.last_second_timestamp) >= 1sec {
+      $state.paperclips.rate = $state.paperclips.current_second_clips
+      $state.paperclips.current_second_clips = 0
+      $state.last_second_timestamp = $now
+    }
+
+    if (($state.paperclips.total > 9) and ($state.autoclippers.count < 1)) and not $state.autoclippers.unlocked {
+      $state.autoclippers.unlocked = true
+      $state.control_line += "; [b]uy autoclipper"
+    }
+
+    # Update display with current game state
+    refresh-game-view $state
+
+    try {
+      let key = job recv --timeout 0sec
+      match $key {
+        "a" => {
+          # TODO: add some way to grow amount?
+          $state = make-paperclip $state 1
+        }
+        "b" => {
+          if $state.money >= $state.autoclippers.cost {
+            $state.money -= $state.autoclippers.cost
+            $state.autoclippers.count += 1
+            $state.autoclippers.cost = ($state.autoclippers.cost * 1.25 | math round)
+          }
+        }
+        "d" => {
+          if $state.paperclips.price > 1 {
+            $state.paperclips.price -= 1
+            $state = update-demand $state
+          }
+        }
+        "q" => {
+          if not $save_exists {
+            $state | save gamestate.nuon
+          } else {
+            $state | save gamestate.nuon --force
+          }
+          print -n "\e[?25h"  # Show cursor before exiting
+          break
+        }
+        "u" => {
+          $state.paperclips.price += 1
+          $state = update-demand $state
+        }
+        "w" => {
+          if $state.money >= $state.wire.cost {
+            $state.wire.length += 1000
+            $state.money -= $state.wire.cost
+          }
+        }
+        _ => {
+          ""
+        }
+      }
+      job spawn { get-user-input }
+    }
+
+    # for 60fps framerate lock
+    sleep 16.666ms
+    let now = date now
+    let delta = $now - $prev
+    $state.delta_time += $delta
+  }
+}