how to use require to include a gem? - ruby

Question

I'm new to Ruby coding. I'm just learning gem/bundle and require. At first, I think the gem should be like jar in Java and pip in Python. So I searched a very simple package named "haha" on rubygems.org -- https://rubygems.org/search?query=haha -- to have a test. But soon I found there always be error and I don't know why. Here's the details --
gem install "haha" -- it runs fine and I found it in the lib folder --
C:\Ruby31-x64\lib\ruby\gems\3.1.0\gems>dir |findstr haha
2022-04-25 17:34 <DIR> haha-1.1.0
2022-04-25 17:34 <DIR> haha-1.2.0
So I think this gem "haha" has been installed successfully.
Then in irb, I tried "require" to include it, then it failes --
irb(main):002:0> require "haha"
C:/Ruby31-x64/lib/ruby/gems/3.1.0/gems/haha-1.2.0/lib/haha/translator.rb:1:in `<top (required)>': uninitialized constant Haha (NameError)
class Haha::Translator
^^^^
Did you mean? Hash
from <internal:C:/Ruby31-x64/lib/ruby/3.1.0/rubygems/core_ext/kernel_require.rb>:85:in `require'
from <internal:C:/Ruby31-x64/lib/ruby/3.1.0/rubygems/core_ext/kernel_require.rb>:85:in `require'
from C:/Ruby31-x64/lib/ruby/gems/3.1.0/gems/haha-1.2.0/lib/haha.rb:1:in `<top (required)>'
from <internal:C:/Ruby31-x64/lib/ruby/3.1.0/rubygems/core_ext/kernel_require.rb>:160:in `require'
from <internal:C:/Ruby31-x64/lib/ruby/3.1.0/rubygems/core_ext/kernel_require.rb>:160:in `rescue in require'
from <internal:C:/Ruby31-x64/lib/ruby/3.1.0/rubygems/core_ext/kernel_require.rb>:149:in `require'
from (irb):2:in `<main>'
from C:/Ruby31-x64/lib/ruby/gems/3.1.0/gems/irb-1.4.1/exe/irb:11:in `<top (required)>'
from C:/Ruby31-x64/bin/irb:33:in `load'
from C:/Ruby31-x64/bin/irb:33:in `<main>'
<internal:C:/Ruby31-x64/lib/ruby/3.1.0/rubygems/core_ext/kernel_require.rb>:85:in `require': cannot load such file -- haha (LoadError)
from <internal:C:/Ruby31-x64/lib/ruby/3.1.0/rubygems/core_ext/kernel_require.rb>:85:in `require'
from (irb):2:in `<main>'
from C:/Ruby31-x64/lib/ruby/gems/3.1.0/gems/irb-1.4.1/exe/irb:11:in `<top (required)>'
from C:/Ruby31-x64/bin/irb:33:in `load'
from C:/Ruby31-x64/bin/irb:33:in `<main>'
I checked the $LOAD_PATH and it looks correct --
irb(main):003:0> pp $LOAD_PATH
["C:/Ruby31-x64/lib/ruby/gems/3.1.0/gems/haha-1.2.0/lib",
"C:/Ruby31-x64/lib/ruby/site_ruby/3.1.0",
"C:/Ruby31-x64/lib/ruby/site_ruby/3.1.0/x64-ucrt",
"C:/Ruby31-x64/lib/ruby/site_ruby",
"C:/Ruby31-x64/lib/ruby/vendor_ruby/3.1.0",
"C:/Ruby31-x64/lib/ruby/vendor_ruby/3.1.0/x64-ucrt",
"C:/Ruby31-x64/lib/ruby/vendor_ruby",
"C:/Ruby31-x64/lib/ruby/3.1.0",
"C:/Ruby31-x64/lib/ruby/3.1.0/x64-mingw-ucrt"]
I think being a package on rubygems this "haha" should be a correct one and it must be my fault somewhere so that I can't "require" it in irb. But I really don't know what's my mistake.
Please kind help.