Can be directly used via straight.el: `(straight-use-package '(unrealscript-mode :repo "https://gist.github.com/RohanHart/201ce875dc4148fa4c3777fbe323c0fe" :local-repo "unrealscript-mode"))`

unrealscript-mode.el

 ;; Unrealscript major mode 

 ;; Copyright (C) 2012  John Connors

 ;; Author: John Connors
 ;; Keywords: extensions

 ;; This file is free software; you can redistribute it and/or modify
 ;; it under the terms of the GNU General Public License as published by
 ;; the Free Software Foundation; either version 2, or (at your option)
 ;; any later version.

 ;; This file is distributed in the hope that it will be useful,
 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 ;; GNU General Public License for more details.

 ;; You should have received a copy of the GNU General Public License
 ;; along with GNU Emacs; see the file COPYING.  If not, write to
 ;; the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 ;; Boston, MA 02111-1307, USA.

 ;;; Commentary:

 ;; 

(defvar unrealscript-mode-hook nil)

(defvar unrealscript-mode-map
  (let ((unrealscript-mode-map (make-sparse-keymap)))
	(define-key unrealscript-mode-map "\C-j" 'newline-and-indent)
	unrealscript-mode-map)
  "Keymap for UNREALSCRIPT major mode")


(defconst unrealscript-font-lock-keywords-1
  (list
   '("\\<\\(?:break\\|c\\(?:\\(?:as\\|ontinu\\)e\\)\\|do\\|e\\(?:lse\\|xtends\\)\\|for\\(?:each\\)?\\|i\\(?:f\\|nterface\\)\\|new\\|return\\|switch\\|var\\|while\\|class\\)\\>" . font-lock-keyword-face))
  "Minimal highlighting expressions for UNREALSCRIPT mode.")

(defconst unrealscript-font-lock-keywords-2
  (append unrealscript-font-lock-keywords-1
		  (list
		   '("\\<\\(?:array\\|b\\(?:ool\\|yte\\)\\|c\\(?:lass\\|o\\(?:erce\\|lor\\|ords\\)\\)\\|de\\(?:faultproperties\\|legate\\)\\|e\\(?:num\\|vent\\)\\|f\\(?:alse\\|loat\\|unction\\)\\|int\\|local\\|name\\|o\\(?:ptional\\|ut\\)\\|plane\\|r\\(?:egion\\|otator\\)\\|st\\(?:ate\\|r\\(?:ing\\|uct\\)\\)\\|true\\|v\\(?:\\(?:a\\|ecto\\)r\\)\\)\\>" . font-lock-keyword-face)))
  "Additional Keywords to highlight in UNREALSCRIPT mode.")


(defconst unrealscript-font-lock-keywords-3
  (append unrealscript-font-lock-keywords-2
		  (list
		   '("\\<\\(?:A\\(?:bstract\\|llowAbstract\\|uto\\(?:Comment\\|ExpandCategories\\)\\)\\|Co\\(?:llapseCategories\\|nfig\\)\\|D\\(?:ep\\(?:endsOn\\|recated\\)\\|isplayName\\|ontCollapseCategories\\)\\|Edit\\(?:Condition\\|InlineNew\\)\\|FriendlyName\\|Hide\\(?:Categories\\|DropDown\\)\\|I\\(?:\\(?:mplemen\\|nheri\\)ts\\)\\|N\\(?:ative\\(?:Replication\\)?\\|o\\(?:Export\\|nTransient\\|t\\(?:EditInlineNew\\|Placeable\\)\\)\\)\\|P\\(?:erObject\\(?:Config\\|Localized\\)\\|laceable\\)\\|ShowCategories\\|T\\(?:oolTip\\|ransient\\)\\|Within\\)\\>" . font-lock-type-face)
		   '("\\<\\(?:auto\\|c\\(?:lient\\|on\\(?:fig\\|st\\)\\)\\|d\\(?:atabinding\\|eprecated\\|uplicatetransient\\)\\|e\\(?:dit\\(?:const\\|fixedsize\\|inline\\(?:use\\)?\\|oronly\\)\\|x\\(?:ec\\|port\\)\\)\\|globalconfig\\|i\\(?:gnores\\|n\\(?:it\\|put\\|stanced\\|terp\\)\\|terator\\)\\|l\\(?:atent\\|ocalized\\)\\|n\\(?:ative\\(?:replication\\)?\\|o\\(?:clear\\|export\\|import\\|ntransactional\\|tforconsole\\)\\)\\|operator\\|p\\(?:o\\(?:\\(?:inte\\|stoperato\\)r\\)\\|r\\(?:eoperator\\|ivate\\|otected\\)\\|ublic\\)\\|re\\(?:liable\\|pnotify\\)\\|s\\(?:erver\\|i\\(?:mulated\\|ngular\\)\\|kip\\|tatic\\)\\|tra\\(?:nsient\\|vel\\)\\|unreliable\\)\\>" . font-lock-keyword-face)
		   '("\\<\\(?:A\\(?:bs\\|cos\\|dd\\(?:Item\\)?\\|llActors\\|s\\(?:c\\|in\\)\\|tan\\)\\|B\\(?:asedActors\\|egin\\(?:Play\\|State\\)\\)\\|C\\(?:aps\\|eil\\|h\\(?:ildActors\\|r\\)\\|l\\(?:amp\\|earTimer\\)\\|o\\(?:\\(?:llidingActor\\)?s\\)\\)\\|D\\(?:estroyed\\|i\\(?:\\(?:sabl\\|vid\\)e\\)\\|ynamicActors\\)\\|E\\(?:mpty\\|n\\(?:\\(?:abl\\|dStat\\)e\\)\\|val\\|xp\\)\\|F\\(?:Clamp\\|M\\(?:ax\\|in\\)\\|Rand\\|astTrace\\|in\\(?:d\\|ish\\(?:Anim\\|Interpolation\\)\\)\\)\\|G\\(?:etTimer\\(?:Count\\|Rate\\)\\|oTo\\(?:State\\)?\\)\\|I\\(?:n\\(?:Str\\|itGame\\|sert\\(?:Item\\)?\\|vert\\)\\|s\\(?:\\(?:InStat\\|TimerActiv\\)e\\)\\)\\|L\\(?:e\\(?:ft\\|n\\|rp\\)\\|o\\(?:cs\\|ge\\)\\)\\|M\\(?:ax\\|i\\(?:rrorVectorByNormal\\|[dn]\\)\\)\\|Normal\\|OverlappingActors\\|P\\(?:o\\(?:pState\\|stBeginPlay\\)\\|reBeginPlay\\|ushState\\)\\|R\\(?:and\\|e\\(?:move\\(?:I\\(?:ndex\\|tem\\)\\)?\\|pl\\(?:ace\\)?\\)\\|ight\\|ound\\)\\|S\\(?:et\\(?:State\\|Timer\\)\\|in\\|leep\\|merp\\|p\\(?:awn\\|lit\\)\\|q\\(?:rt\\|uare\\)\\)\\|T\\(?:an\\|ick\\|ouchingActors\\|race\\(?:Actors\\)?\\)\\|V\\(?:Rand\\|Size\\|isible\\(?:\\(?:Colliding\\)?Actors\\)\\)\\|\\(?:ro\\|vec\\)t\\)\\>" . font-lock-function-name-face)))
  "Balls-out highlighting in UNREALSCRIPT mode.")

(defvar unrealscript-font-lock-keywords unrealscript-font-lock-keywords-3
  "Default highlighting expressions for UNREALSCRIPT mode.")


(defvar unrealscript-indent-width 4)

(defun looking-at-unrealscript-indent-keyword ()
  (or (looking-at "^[\t ]*while") (looking-at "^[ \t]*foreach") (looking-at "^[ \t]*do") (looking-at "^[\t ]*if") (looking-at "^[\t ]*else") (looking-at "^[\t ]*for")))

(defun looking-at-unrealscript-block-end ()	 
  (or (looking-at "^[\t ]*end") (looking-at "^[\t ]*break[\t ]*;") (and (looking-at "^.*};*[ \t]*$") (not (looking-at "^.*{")))))

(defun looking-at-unrealscript-block-start ()
  (or (looking-at "^[\t ]*begin") (looking-at "^[\t ]*default[\t ]*:") (looking-at "^[\t ]*case.*:") (and (looking-at "^.*{") (not (looking-at "^.*};*[ \t]*$")))))

;; Function to control indenting.
(defun unrealscript-indent-line ()
  "Indent current line as Unrealscript code"
  (interactive)
  ;; Set the point to beginning of line.
  (beginning-of-line)
  (if (bobp)
	  (indent-line-to 0)
	(let ((not-indented t) (lines-back 0) cur-indent)
	  (if	 (looking-at-unrealscript-block-end) ; Check for closing brace
		  ;; if we are at the end of a block
		  (progn
			(save-excursion
			  (forward-line -1)
			  (setq lines-back (+ lines-back 1))
			  (setq cur-indent (- (current-indentation) unrealscript-indent-width)))
			;; Safety check to make sure we don't indent negative.
			(if (< cur-indent 0)
				(setq cur-indent 0)))
		;; else scan backward 
		(save-excursion
		  (if (looking-at-unrealscript-block-start) ; Opening block			  
			  (progn
		            	;; scan back to start of previous non-empty line
                	    	(skip-chars-backward "\n[:space:]")
                	    	(move-beginning-of-line nil)

				(setq lines-back (+ lines-back 1))
				(setq cur-indent (current-indentation))
				(setq not-indented nil))
			(while not-indented
			  (forward-line -1)
			  (setq lines-back (+ lines-back 1))
			  (if (looking-at-unrealscript-block-end) ;; Closing Block
				  (progn
					(setq cur-indent (current-indentation))
					(setq not-indented nil))
				(if (looking-at-unrealscript-block-start)
					(progn
					  (setq cur-indent (+ (current-indentation) unrealscript-indent-width))
					  (setq not-indented nil))
				  (if (looking-at-unrealscript-indent-keyword)
					  (progn
						(setq cur-indent (current-indentation))
						(forward-line 1)
						(setq lines-back (- lines-back 1))
						(if (looking-at-unrealscript-block-start)
							(setq not-indented nil) ;; has block
						  (if (zerop lines-back) ;; no block
							  (progn
								(setq cur-indent (+ cur-indent unrealscript-indent-width))						 
								(setq not-indented nil))
							(setq not-indented nil))))
					(if (bobp)
						(setq not-indented nil)))))))))
	  (if cur-indent
		  (indent-line-to cur-indent)
		(indent-line-to 0))))) 

(defun unrealscript-populate-syntax-table (table)
  "Populate the given syntax table as necessary for a C-like language.
This includes setting ' and \" as string delimiters, and setting up
the comment syntax to handle both line style \"//\" and block style
\"/*\" \"*/\" comments."

  (modify-syntax-entry ?_	 "_"	   table)
  (modify-syntax-entry ?\\ "\\"	   table)
  (modify-syntax-entry ?+	 "."	   table)
  (modify-syntax-entry ?-	 "."	   table)
  (modify-syntax-entry ?=	 "."	   table)
  (modify-syntax-entry ?%	 "."	   table)
  (modify-syntax-entry ?<	 "."	   table)
  (modify-syntax-entry ?>	 "."	   table)
  (modify-syntax-entry ?&	 "."	   table)
  (modify-syntax-entry ?|	 "."	   table)
  (modify-syntax-entry ?\' "\""	   table)
  (modify-syntax-entry ?\240 "."	 table)

  ;; Set up block and line oriented comments.	 The new C
  ;; standard mandates both comment styles even in C, so since
  ;; all languages now require dual comments, we make this the
  ;; default.
  (modify-syntax-entry ?/	 ". 124b" table)
  (modify-syntax-entry ?*	 ". 23"	table)

  (modify-syntax-entry ?\n "> b"	table)
  ;; Give CR the same syntax as newline, for selective-display
  (modify-syntax-entry ?\^m "> b" table)
  table)

(defvar unrealscript-mode-syntax-table
  (let ((unrealscript-mode-syntax-table (unrealscript-populate-syntax-table (make-syntax-table))))
	unrealscript-mode-syntax-table)
  "Syntax table for unrealscript-mode")

(defun unrealscript-mode ()
  "Major mode for editing Unrealscript files"
  (interactive)
  (kill-all-local-variables)
  (set-syntax-table unrealscript-mode-syntax-table)
  (use-local-map unrealscript-mode-map)
  (setq indent-line-function 'unrealscript-indent-line)
  (setq font-lock-defaults '(unrealscript-font-lock-keywords nil t))
  (setq major-mode 'unrealscript-mode)
  (setq mode-name "UNREALSCRIPT")
  (run-hooks 'unrealscript-mode-hook)
  (setq case-fold-search t)
  (setq font-lock-keywords-case-fold-search t))


(provide 'unrealscript-mode)