Half-Life is keyed in every way shape and form, the original game is actually my #1 favorite of all time and I can literally play it forever and ever, the expansions are really fun as well that expand the Black Mesa incident to a greater scale. The second game and its episodes are lesser IMO but are still 9/10s.
Valve's theme that you hear in the start of all of their games is actually just the theme from midway through Surface Tension, the longest chapter of HL1. Man the game's cinematics are still incredible today for a 20 year old game, like the tentacle in Blast Pit, the jets in Surface Tension. It's just incredible really I implore you play it; the game really set the bar for what a good singleplayer FPS is while still feeling...