- Improve Merge function, thanks dzaima!

- Spawn now spawns a random 4 with a 10% chance
- Fix crash when using an invalid key
- Fix cursor not being restored properly

2048.bqn

@@ -3,34 +3,34 @@
 # h: left, j: down, k: up, l: right
 # it needs a VT-100 compatible terminal
 
-Merge←{ # Merges a row of tiles to the right
-  moved←4⊸↑⌾⌽ 0⊸≠⊸/𝕩 # remove empty tiles to move the tiles as far as possible
-  m←⌽0∾˜(¬⊸∧`=˝˘)⌾⌽2↕moved # which tiles to merge
-  r←(⟨∞⟩){t←⊑m ⋄ m↩1↓m ⋄ t◶⟨𝕨∾𝕩,(¯1↓𝕨)∾𝕩+¯1⊑𝕨⟩@}˜´moved # Merge tiles
-  4⊸↑⌾⌽⌽∞⊸≠⊸/r # Resize the result
-}
-Step←>·Merge¨<˘   # Merges each row of the board
-Up←Step⌾(⌽⍉∘⌽)    # Each direction merges the board
-Down←Step⌾⍉       # by rotating it to the correct orientation, merging the rows and reversing the rotation
+Merge←{𝕩 0⊸≠⊸/↩ ⋄ m←<`=⟜«𝕩 ⋄ 4↑(¬»m)/𝕩×1+m}⌾⌽ # Merge a single row to the right
+Step←Merge˘    # Merges each row of the board
+Up←Step⌾(⌽⍉∘⌽) # Each direction merges the board
+Down←Step⌾⍉    # by rotating it to the correct orientation, merging the rows and reversing the rotation
 Right←Step
 Left←Step⌾(⌽˘)    
-Spawn←{i←(•rand.Range∘≠⊑⊢)(0⊸= /○⥊ ↕∘≢)𝕩 ⋄ 2˙⌾(i⊸⊑) 𝕩} # Spawns a 2 at a random empty position
+Spawn←{i←•rand.Range∘≠⊸⊑(0⊸= /○⥊ ↕∘≢)𝕩 ⋄ (•rand.Range∘≠⊸⊑9‿1/2‿4)⌾(i⊸⊑) 𝕩} # Spawns a 2 or a 4 (10% chance) at a random empty position
 Lose←Left∘Right∘Down∘Up⊸≡ # Losing condition, no moves change the board
 Win←∨´·∨˝2048⊸= #  Winning condition, 2048!
 
 board←Spawn 4‿4⥊0
 e←@+27
-•term.RawMode 1 # 
+•term.RawMode 1 
+Quit←{•Out e∾"[?12l"∾e∾"[?25h" ⋄ •Exit 𝕩}
 •Out e∾"[?25l"∾e∾"[2J"∾e∾"[H" # Cursor to origin, hide it and clear screen
 {𝕤⋄
-    •Out e∾"[H" # Cursor to origin
+    •Out e∾"[H"∾e∾"[2J" # Cursor to origin
     •Out "Controls: h: left, j: down, k: up, l: right, q: quit"
     •Show board 
+
     key←•term.CharB @ # Read key
-    {𝕤⋄•Out e∾"[?12l"∾e∾"[?25h"⋄•Exit 0}⍟(key='q')@ # Quit key?
-    move←⊑(key="hjkl")/Left‿Down‿Up‿Right # Get movement function from the key
-    {𝕤⋄board↩Spawn∘Move 𝕩}⍟(Move⊸≢) board # Generate the next board if the move is valid
-    {𝕤⋄•Out "You win!" ⋄ •Exit 0}⍟Win board
-    {𝕤⋄•Out "You lose!" ⋄ •Exit 1}⍟Lose board
+    ⊑key∊"hjklq"?
+      {𝕤⋄•Out e∾"[?12l"∾e∾"[?25h"⋄ Quit 0}⍟(key='q')@ # Quit key?
+      move←⊑(key="hjkl")/Left‿Down‿Up‿Right # Get movement function from the key
+      {𝕤⋄board↩Spawn∘Move 𝕩}⍟(Move⊸≢) board # Generate the next board if the move is valid
+      •Out e∾"[H" # Cursor to origin
+      •Show board 
+      {𝕤⋄•Out "You win!" ⋄ Quit 0}⍟Win board
+      {𝕤⋄•Out "You lose!"⋄ Quit 1}⍟Lose board
+    ; @
 }•_While_{𝕤⋄¬Lose board}@
-•Out e∾"[?12l"∾e∾"[?25h" # Restore the cursor