diff --git a/dot_config/fish/conf.d/you_should_use.fish b/dot_config/fish/conf.d/you_should_use.fish
new file mode 100644
index 0000000..6053b01
--- /dev/null
+++ b/dot_config/fish/conf.d/you_should_use.fish
@@ -0,0 +1,14 @@
+set --global FISH_YOU_SHOULD_USE_VERSION "1.2.0"
+
+__ysu__set_default NONE (set_color normal)
+__ysu__set_default BOLD (set_color -o normal)
+__ysu__set_default RED (set_color red)
+__ysu__set_default YELLOW (set_color yellow)
+__ysu__set_default VIOLET (set_color magenta)
+
+set --global YSU__MESSAGE_POSITION "after"
+set --global YSU__HARDCORE_MODE false
+
+functions -q __ysu__check_aliases
+functions -q __ysu__check_git_aliases
+functions -q __ysu__flush_buffer
diff --git a/dot_config/fish/functions/__ysu__check_aliases.fish b/dot_config/fish/functions/__ysu__check_aliases.fish
new file mode 100644
index 0000000..45432fa
--- /dev/null
+++ b/dot_config/fish/functions/__ysu__check_aliases.fish
@@ -0,0 +1,24 @@
+function __ysu__check_aliases \
+        --on-event fish_preexec
+    string match --quiet "sudo *" "$argv"; and return
+
+    set --local found false
+    alias | sort | while read entry
+        set entry (string replace "=" "" "$entry")
+        set --local tokens (string split --max 2 " " "$entry")
+        set --local key "$tokens[2]"
+        set --local escaped_key (string escape --no-quote --style=regex "$key")
+
+        string match --quiet --regex "$escaped_key" "$YSU__IGNORED_GLOBAL_ALIASES"; and continue
+
+        set --local value (string replace --regex '(?:[\"|\']([^,]*)[\"|\'])' '$1' "$tokens[3]")
+        set --local escaped_value (string escape --no-quote --style=regex "$value")
+
+        if string match --quiet --regex "(?<=^|\s)$escaped_value(?=\s|\$)" "$argv"
+            __ysu__message "alias" "$value" "$key"
+            set found true
+        end
+    end
+
+    "$found"; and __ysu__check_hardcore
+end
diff --git a/dot_config/fish/functions/__ysu__check_git_aliases.fish b/dot_config/fish/functions/__ysu__check_git_aliases.fish
new file mode 100644
index 0000000..6fed729
--- /dev/null
+++ b/dot_config/fish/functions/__ysu__check_git_aliases.fish
@@ -0,0 +1,23 @@
+function __ysu__check_git_aliases \
+        --on-event fish_preexec
+    string match --quiet "sudo *" "$argv"; and return
+
+    if string match --quiet --regex "git *" "$argv"
+        set --local found false
+        git config --get-regexp "^alias\..+\$" | sort | while read key value
+            set key (string split --max 2 "." "$key")[2]
+            set --local escaped_key (string escape --no-quote --style=regex "$key")
+
+            string match --quiet --regex "$escaped_key" "$YSU__IGNORED_GIT_ALIASES"; and continue
+
+            set --local escaped_value (string escape --no-quote --style=regex "$value")
+
+            if string match --quiet --regex "git $escaped_value(?=\s|\$)" "$argv"
+                __ysu__message "git alias" "$value" "git $key"
+                set found true
+            end
+        end
+
+        "$found"; and __ysu__check_hardcore
+    end
+end
diff --git a/dot_config/fish/functions/__ysu__check_hardcore.fish b/dot_config/fish/functions/__ysu__check_hardcore.fish
new file mode 100644
index 0000000..1f11de8
--- /dev/null
+++ b/dot_config/fish/functions/__ysu__check_hardcore.fish
@@ -0,0 +1,6 @@
+function __ysu__check_hardcore
+    if "$YSU__HARDCORE_MODE"
+        __ysu__write_buffer \
+            "$BOLD$RED​You Should Use hardcore mode enabled. Use your aliases!"
+    end
+end
diff --git a/dot_config/fish/functions/__ysu__flush_buffer.fish b/dot_config/fish/functions/__ysu__flush_buffer.fish
new file mode 100644
index 0000000..a6828db
--- /dev/null
+++ b/dot_config/fish/functions/__ysu__flush_buffer.fish
@@ -0,0 +1,8 @@
+function __ysu__flush_buffer \
+        --on-event fish_prompt
+    if test -n "$__BUFFER"
+        printf "$__BUFFER"
+    end
+
+    set __BUFFER ""
+end
diff --git a/dot_config/fish/functions/__ysu__get_field.fish b/dot_config/fish/functions/__ysu__get_field.fish
new file mode 100644
index 0000000..daeca0c
--- /dev/null
+++ b/dot_config/fish/functions/__ysu__get_field.fish
@@ -0,0 +1,4 @@
+function __ysu__get_field \
+        --argument-names dict key
+    eval echo \$$dict'__'$key
+end
diff --git a/dot_config/fish/functions/__ysu__message.fish b/dot_config/fish/functions/__ysu__message.fish
new file mode 100644
index 0000000..aa5e820
--- /dev/null
+++ b/dot_config/fish/functions/__ysu__message.fish
@@ -0,0 +1,7 @@
+function __ysu__message \
+        --argument-names alias_type command alias
+    # zero-width space delinates the end of a variable and the beginning of the message
+    __ysu__write_buffer "\
+$BOLD$YELLOW​Found existing $alias_type for \"$VIOLET$command$YELLOW\".
+You should use: \"$alias\"\n"
+end
diff --git a/dot_config/fish/functions/__ysu__set_default.fish b/dot_config/fish/functions/__ysu__set_default.fish
new file mode 100644
index 0000000..7de37bf
--- /dev/null
+++ b/dot_config/fish/functions/__ysu__set_default.fish
@@ -0,0 +1,7 @@
+function __ysu__set_default \
+        --no-scope-shadowing \
+        --argument-names var default
+    if not set -q "$var"
+        set --global "$var" "$default"
+    end
+end
diff --git a/dot_config/fish/functions/__ysu__set_field.fish b/dot_config/fish/functions/__ysu__set_field.fish
new file mode 100644
index 0000000..9df9fb1
--- /dev/null
+++ b/dot_config/fish/functions/__ysu__set_field.fish
@@ -0,0 +1,4 @@
+function __ysu__set_field \
+        --argument-names dict key value
+    set --global $dict'__'$key $value
+end
diff --git a/dot_config/fish/functions/__ysu__write_buffer.fish b/dot_config/fish/functions/__ysu__write_buffer.fish
new file mode 100644
index 0000000..c2ccc0e
--- /dev/null
+++ b/dot_config/fish/functions/__ysu__write_buffer.fish
@@ -0,0 +1,18 @@
+function __ysu__write_buffer \
+        --argument-names contents
+    set --global __BUFFER "$contents$__BUFFER\n"
+
+    set --local position "before"
+    if set -q YSU__MESSAGE_POSITION
+        set position "$YSU__MESSAGE_POSITION"
+    end
+
+    if [ "$position" = "before" ]
+        __ysu__flush_buffer
+    else if [ "$position" != "after" ]
+        echo "\
+$RED$BOLD​Unknown value for MESSAGE_POSITION $YSU__MESSAGE_POSITION
+Expected value 'before' or 'after'"
+        __ysu__flush_buffer
+    end
+end