Half-Life is simply one of my top favorite games!
I loved this game so much that I am trying to learn how to speedrun it!
My first play-through wasn't the greatest and I didn't really enjoy the game that much,
but my second, third and fourth play-throughs were so fun this game became my all time favorites!
I will recommend you this game if you are looking for a fun linear first person shooter with a bit of a twist to it!
Here are my thoughts and opinions of this game's properties:
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Story is really interesting (10/10)
>> I do not want to spoil the story for you so I will try to minimize as much as I can.
>> You learn about the Black Mesa facility as you play through and discover its darkest secrets!
>> Your character is for you to design as of the main character is silent and lets you design his personality!
>> The first game starts with lots of mysteries that makes you thing about what is going on and how?
>> The story is intriguing and cool, really worth following!

Enemies are perfectly made (10/10)
>> There is a big variety of enemies(for its time) with really interesting properties and mechanics!
>> The enemies are balanced well and 'realistically' with their difficulty levels!
>> Most enemies are a pain to deal with and because of that it makes you thing before you run blindly into a room!
>> Every enemy feels unique and fresh when encountered at first!

Movement is great (9/10)
>> I really love the movement and its flaws!
>> The movement is so different then other games that it took me a while to get used to it!
>> One of the best things about HL's movement is that you can preform a glitch called B-HOP,
of which you strafe from side to side and can gain lot's of speed it preformed correctly!
>> This game's movement really gives you a feel of freedom!

Weapons are so fun to use (9/10)
>> It's safe to say that Half-Life got more then enough weapon variety!
>> This game has so many different and useful weapons its ridiculous!
>> Every weapon feels unique and new upon coming across!
>> Almost until the very end of the game every weapon got its purpose!

Sounds are so well done its ridiculous (9/10)
>> The sounds fit the game and its age well.
>> Some sounds are annoying but I grew to love them so much that I just make them in-game for fun!
>> Not all the sounds are too repetitive, but some are.

Level design is very good (9/10)
>> The levels aren't too difficult and definitely make you think about your next move.
>> The level's have lots of interactability although they are linear!
>> The levels also were designed to teach you how to play the game without you noticing!
>> The maps aren't too strict and you can find glitches very easily (if you look for them and it's very good for speedrunning)

Graphics are really good for their time (9/10)
>> Those graphics really fit well the game and its vibe!
>> There aren't too many empty/boring places to look at!
>> I really like the pixelated graphics, I believe they look cool!
>> It also shows very well the history and the evolution of videogames' graphics!

Puzzles are difficult at first (9/10)
>> I had trouble solving some of the puzzles of this game at my first play-through.
>> They force you to take a step back and explore the maps a bit more.
>> I just wish they made it a tiny bit more clear to how to solve those puzzles.

Soundtracks are a fine -> (9/10)
>> The tracks are fitting very well with the atmosphere!
>> The music sounds very good even for today's standards!
>> The music will also change depending on the environment and situation most of the time.
>> My only complaint is that we don't get to hear more of it...

AI is simple yet complex (8/10)
>> Its really difficult to explain but the AI feels slow and unresponsive and also so responsive at the same time.
>> I can just guess its the animations that hold back the AI so much, because entities can make only one action at a time.
>> Although the AI is slow it gives a great opportunity to shoot the enemies while they are running or rotating.

Game's setting/atmosphere are okay (8/10)
>> The setting of this game aim's towards scientific disaster and it does that very nicely!
>> Throughout the game the setting will change and some settings I didn't really like or found interesting as others...
>> Valve(Creators of Half-Life) did a good job on the atmosphere but I feel that in some levels they changed it too much...

Combat was executed well (8/10)
>> Some of the enemies are more difficult than other and balanced fairly 'realistic' for combat.
>> There are lots of options of how to kill your enemies or friends.
>> The melee weapon(crowbar) in Half-Life has a real useful purpose in game!
not many games have useful melee weapons which is a shame.
>> All 'Movement, Weapons and Enemies' are balanced for a difficult experience at first, but after playing the game and getting the hang of the combat system, it becomes much easier!

Game's cons:
- The movement is very uncomfortable at the beginning and climbing ladders is hell because of that.
- Some NPCs will have trouble following you.
- Some hitboxes are really weird and can hurt the flow of the gameplay!

Side comments/notes:
- Abusing this game's glitches are very fun for speedrunning or playing through it in general!
- Some NPCs are very funny and have interesting 'personalities'!
- The boss/enemy introductions are always well executed and smooth!
- the game also always keeps you on your toes!

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So after all of this I will rate this amazing game a solid (10/10)