diff --git a/bat.sh b/bat.sh
index c5a0056..e78280b 100755
--- a/bat.sh
+++ b/bat.sh
@@ -1,15 +1,19 @@
 #!/usr/bin/bash
 
+set -euo pipefail
+
 # Detect fish shell and ask user to switch to bash (bash-only syntax)
-if [ -n "${FISH_VERSION:-}" ] || case "$SHELL" in *fish*) ;; *) false ;; esac; then
+if [ -n "${FISH_VERSION:-}" ] || case "${SHELL:-}" in *fish*) ;; *) false ;; esac; then
   echo "Warning: fish shell detected."
   echo "This script is written for bash and may have syntax issues under fish."
   echo "Please switch to bash first and re-run it, e.g.: bash $0"
-  read -r -p "Press Enter to continue anyway, or Ctrl+C to cancel..." </dev/tty || true
+  if [ -t 0 ] && [ -e /dev/tty ]; then
+    read -r -p "Press Enter to continue anyway, or Ctrl+C to cancel..." </dev/tty || true
+  fi
 fi
 
 skip_watermark=false
-if [ "$1" = "--skip-watermark" ]; then
+if [ "${1:-}" = "--skip-watermark" ]; then
   skip_watermark=true
 fi
 
@@ -23,8 +27,8 @@ if [ "$skip_watermark" = false ]; then
             |___/
 
     --------------- bat Install Script ---------------
-  BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE UNDER THE GPL-2.0 LICENCE, THERE IS NO WARRANTY
-  FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. See the LICENCE for more detail
+  BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE UNDER THE GPL-2.0 LICENSE, THERE IS NO WARRANTY
+  FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. See the LICENSE for more detail
 '
 fi
 
@@ -50,20 +54,24 @@ if ! command -v git >/dev/null || ! command -v curl >/dev/null || ! command -v w
 fi
 
 # Install bat
-fresh_bat_install=false
 if ! command -v bat >/dev/null && ! command -v batcat >/dev/null; then
   if command -v pacman >/dev/null; then
     echo "pacman detected. Installing bat"
-    sudo pacman -S --needed --noconfirm bat bat-extras
+    if ! sudo pacman -S --needed --noconfirm bat bat-extras; then
+      echo "Failed to install bat. Install it manually, then re-run this script."
+      exit 1
+    fi
   elif command -v apt >/dev/null; then
     echo "apt detected. Installing bat"
-    sudo apt install bat -y
+    if ! sudo apt install bat -y; then
+      echo "Failed to install bat. Install it manually, then re-run this script."
+      exit 1
+    fi
   else
     echo "No supported package manager found (pacman/apt)."
     echo "Please install bat manually, then re-run this script."
     exit 1
   fi
-  fresh_bat_install=true
 fi
 
 # Debian/Ubuntu ship the binary as batcat, provide bat for the commands below
@@ -76,38 +84,45 @@ if ! command -v bat >/dev/null; then
   exit 1
 fi
 
-if [ "$fresh_bat_install" = true ]; then
-  # 1. Detect the actual active shell name (not just the login default)
-  CURRENT_SHELL=$(basename -- "$SHELL")
-
-  # 2. Source the correct configuration file safely
-  if [ "$CURRENT_SHELL" = "bash" ] && [ -f ~/.bashrc ]; then
-    source ~/.bashrc
-  elif [ "$CURRENT_SHELL" = "zsh" ] && [ -f ~/.zshrc ]; then
-    source ~/.zshrc
-  elif [ "$CURRENT_SHELL" = "fish" ] && [ -f ~/.config/fish/config.fish ]; then
-    source ~/.config/fish/config.fish
-  else
-    echo "Unsupported or unreadable shell configuration: $CURRENT_SHELL"
+# Install the Catppuccin Mocha theme (downloaded and configured names must match)
+BAT_CONFIG_DIR="$(bat --config-dir)"
+mkdir -p "$BAT_CONFIG_DIR/themes"
+if [ ! -f "$BAT_CONFIG_DIR/themes/Catppuccin Mocha.tmTheme" ]; then
+  if ! wget -q -O "$BAT_CONFIG_DIR/themes/Catppuccin Mocha.tmTheme" \
+    "https://github.com/catppuccin/bat/raw/main/themes/Catppuccin%20Mocha.tmTheme"; then
+    echo "Failed to download the Catppuccin Mocha theme."
+    exit 1
   fi
-
 fi
-
-# Install Catppuccin themes
-source ~/.bashrc
-mkdir -p "$(bat --config-dir)/themes"
-wget -P "$(bat --config-dir)/themes" https://github.com/catppuccin/bat/raw/main/themes/Catppuccin%20Macchiato.tmTheme
 bat cache --build
 
-echo "--theme="Catppuccin Mocha"" >>"$(bat --config-dir)/themes"
+# Set the default theme in bat's config file (the themes/ directory only holds themes)
+if ! grep -qxF -- '--theme="Catppuccin Mocha"' "$BAT_CONFIG_DIR/config" 2>/dev/null; then
+  printf '%s\n' '--theme="Catppuccin Mocha"' >>"$BAT_CONFIG_DIR/config"
+fi
 
-# Detect shell name via POSIX standard
-CURRENT_SHELL=$(basename "$0" 2>/dev/null || echo "$0")
-CURRENT_SHELL="${CURRENT_SHELL#-}"
+# Configure the MANPAGER for the user's actual login shell ($SHELL, not $0)
+CURRENT_SHELL=$(basename -- "${SHELL:-/bin/bash}")
 
 case "$CURRENT_SHELL" in
-"bash") [ -f ~/.bashrc ] && echo "export MANPAGER="bat -plman"" >>~/.bashrc ;;
-"zsh") [ -f ~/.zshrc ] && echo "export MANPAGER="bat -plman"" >>~/.zshrc ;;
-"fish") exec fish -c "echo "export MANPAGER="bat -plman"" >> ~/.config/fish/config.fish" ;;
-*) echo "Unsupported shell: $CURRENT_SHELL" ;;
+bash)
+  if [ -f "$HOME/.bashrc" ] && ! grep -qxF 'export MANPAGER="bat -plman"' "$HOME/.bashrc"; then
+    printf '%s\n' 'export MANPAGER="bat -plman"' >>"$HOME/.bashrc"
+  fi
+  ;;
+zsh)
+  if [ -f "$HOME/.zshrc" ] && ! grep -qxF 'export MANPAGER="bat -plman"' "$HOME/.zshrc"; then
+    printf '%s\n' 'export MANPAGER="bat -plman"' >>"$HOME/.zshrc"
+  fi
+  ;;
+fish)
+  if [ -f "$HOME/.config/fish/config.fish" ] && ! grep -qxF 'set -gx MANPAGER "bat -plman"' "$HOME/.config/fish/config.fish"; then
+    printf '%s\n' 'set -gx MANPAGER "bat -plman"' >>"$HOME/.config/fish/config.fish"
+  fi
+  ;;
+*)
+  echo "Unsupported shell: $CURRENT_SHELL (skipping MANPAGER setup)"
+  ;;
 esac
+
+echo "bat configured with the Catppuccin Mocha theme."