tree-puzzle: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/tree-puzzle - from package: tree-puzzle

You may install the required package with command apt-get install {package}

Error in other languages:
tree-puzzle: bevel nie gevind nie
tree-puzzle: comandă negăsită
tree-puzzle: comando não encontrado
tree-puzzle: commande introuvable
tree-puzzle: command not found
tree-puzzle: käsku ei ole
tree-puzzle: không tìm thấy lệnh
tree-puzzle: komanda nerasta
tree-puzzle: Kommando nicht gefunden.
tree-puzzle: kommandot finns inte
tree-puzzle: komut yok
tree-puzzle: nie znaleziono polecenia
tree-puzzle: níor aimsíodh an t-ordú
tree-puzzle: no se encontró la orden
tree-puzzle: no s'ha trobat l'ordre
tree-puzzle: opdracht niet gevonden
tree-puzzle: parancs nem található
tree-puzzle: perintah tidak ditemukan
tree-puzzle: príkaz nenájdený
tree-puzzle: příkaz nenalezen
tree-puzzle: команда не найдена
tree-puzzle: командата не е открита
tree-puzzle: 命令找不到
tree-puzzle: コマンドが見つかりません