_______________________
| |         |    /    \ |
| |_________|    \____/ |
|                       |
| _____   _____   _____ |
||key1 | |key2 | |key3 ||
||_____| |_____| |_____||
| _____   _____   _____ |
||key4 | |key5 | |key6 ||
||_____| |_____| |_____||
| _____   _____   _____ |
||key7 | |key8 | |key9 ||
||_____| |_____| |_____||
| _____   _____   _____ |
||key11| |key13| |key12||
||_____| |_____| |_____||
|_______________________|