what's I missed lead to building failed?

[andyyuan78]

ubgpu@ubgpu:/github$
ubgpu@ubgpu:/github$
ubgpu@ubgpu:/github$ git clone https://github.com/outerWorld/snail.git
Cloning into 'snail'...
remote: Counting objects: 371, done.
remote: Total 371 (delta 0), reused 0 (delta 0), pack-reused 371
Receiving objects: 100% (371/371), 75.76 MiB | 4.71 MiB/s, done.
Resolving deltas: 100% (141/141), done.
Checking connectivity... done.
ubgpu@ubgpu:/github$ cd snail/
ubgpu@ubgpu:/github/snail$ make
g++ -c -o src/sn_wordic.o src/sn_wordic.cpp
src/sn_wordic.cpp:13:20: fatal error: common.h: No such file or directory
#include "common.h"
^
compilation terminated.
make: *** [src/sn_wordic.o] Error 1
ubgpu@ubgpu:/github/snail$
ubgpu@ubgpu:~/github/snail$