$2    _____   $1_____$2
  -'     '-$1|     |$2
 /     ___ $1|     |$2
|     / _ \$1|_____|$2
'    / /_\ \
 \  / _____ \$4___
  $3|$2/_/  $3|   $4|   |
  $3|     |   $4|___|
  $3|_____|