Scoring kills earns the player permanent money to buy weapons, like guns and grenades. Using game points (GASH for Hong Kong and Taiwan), players can also buy more weapons, for example, the SACR (Steyr ACR) can be only bought with game points.
In 2020, the Cinor Empire was invading other countries and became a large empire. They used ruthless ways to invade other countries, causing patriots to form a rebellion called Kronoc. The Kronoc rebels hired bio-engineered mercenaries from a wealthy company called Asin, forming the Kronoc Army. The Cinor Empire also hired bio-engineered mercenaries to counterattack the rebel army.
There are many kinds of weapons in the game, including assault rifles, submachine guns, shotguns and pistols.
- Assault rifles: Assault rifles (commonly abbreviated as "AR") are balanced weapons that most players use. Each newly created character comes with an assault rifle. An example of an assault rifle in the game is the French PAMAS (FAMAS) assault rifle, the Russian AK-74, the American M4A1, or the Korean K2.
- Machine guns: Machine guns (commonly abbreviated as "MG") are most effective for close quarter battles. In the game, most of the machine guns have 100 bullets, but some weapons that are paid in GASH points have more than 100 bullets and the Amell weapon in the game have 300 bullets. In the Taiwan version of the game, players call machine guns as the "God of Battles".
- Pistols: Pistols are a kind of subarms in the game. Examples of pistols in the game include the Taurus Raging Bull revolver (named simply "Raging Bull" in-game) and the Beretta 92FS semi-automatic pistol. (named "ES92FS" in-game)
- Shotguns: Shotguns are a kind of subarms too, like pistols. Unlike pistols, shotguns are more effective when used in close quarter battles.
- Submachine guns: Submachine guns (commonly abbreviated as "SMG") are more effective in close quarter battles. Although it does not have the high damage of a Machine Gun, nor the accuracy of an Assault Rifle, its light weight and high rate of fire makes it a favourite weapon for firefights in dangerous enclosed areas where players must keep moving to minimize the chance of being hit.
- Sniper rifles: Sniper rifles are long range weapons. Players can only see a crosshair when they are using the scope. In the Hong Kong version of the game, players used to call the SL96 (L96A1) in the game as "210". This is because it deals 210 damage, usually causing instant kill even the victim is shot in non-lethal areas.
- Knives: Knives are issued to every player in the game. Similar to the game Counter-Strike, players usually draw their knives out while walking. Due to the light weight of knives, players can move faster. Knives are not purchasable in the game, but knives will upgrade later, for example, knives will be upgraded to swords when the player is promoted to a general.
- Grenades: Grenades include frag grenades, flashbangs and smoke grenades.
Heat Project uses a rank system, players can upgrade their characters with experience points into different ranks, including Private to General. When players are promoted to another rank, they can gain "technique points", which they can use it to learn some special techniques.
Experience points are calculated by the players numbers of kills, deaths and how many rounds did they win and lose. When defeating opponents with more high level than the player, they will gain more experience points.
There are several ways to customize the player's character, for example, players can change their clothes to other uniforms, for example, Christmas suits, camouflage suits and police uniforms are available. Players can also customize their hair color and character's size. (big and small) 
Official gameplay modes 
- Mission Combat - In Mission Combat mode, A team must plant a bomb at one of the bombsites. If the bomb is not planted after 4 minutes, B team will win automatically. It takes 40 seconds to plant or disarm a bomb. Another way to win is to eliminate all players of the opposition team. Players who are killed cannot respawn until the next round.
- Team Death Match - The objective of team deathmatch is to kill 50 or 100 players of the opposite team (decided by the host), players will be divided into two teams (A team and B team). this game can be set into 50 kills or 100 kills until game end. Deathmatch only maps include "Death Room" and some other maps. But all maps can be used for deathmatch and team deathmatch.
- Unlimited Combat - Players will be spawned in different locations in this mode. The game will end when there are 50 or 100 deaths (decided by the host). Deathmatch only maps include "Four Room" and some other maps. But all maps can be used for deathmatch and team deathmatch.
Player-made game modes
Players have created some game modes by themselves, including knife wars and more.
- Knife Warfare - In Knife Warfare, players can only use a knife, sometimes, people also have some other rules, including "1 versus 1 only" or "Count 3 before dueling".
- Subarm Battle - In Subarm Battle, players can only use subarms and knives, that means pistols, shotguns and knives.
- Sniping Servers - Players can only use sniper rifles, subarms (like shotguns and pistols) and knives.
- Bug Mode - In this mode, people exploit bugs in maps, they are (usually) free to do everything, except killing, but sometimes, players break the rules and use speed hacks.
In Heat Project, there are still some bugs and glitches. For example, in the "Snowland" map, players can walk up the unreachable mountain to snipe enemy players, and in the "Alcatraz Island" map, players can also jump outside the map boundaries.
In July, players in the Hong Kong version of Heat Project are exploiting a glitch to edit guns, they released the program and called it "改槍為王" (literally, "Editing guns is the only way") and named it "哈哈哈.exe". ("Hahaha.exe"), also, it's usually bundled with hex editors. The hack enabled some hackers to edit their guns into better guns, like unreleased guns that are only in other localized versions. (for example, the Dragunov sniper rifle and smoke grenades)
In about 2006 quarter four, an unknown developer made a hack named "捉蟲皇后" (literally, "debugging queen"), then the same developer released popular hacks named with an "egg" theme like "阿婆鐵蛋" and "阿伯龜蛋". (lit. Grandma's Metal Egg, Grandpa's Turtle Egg) These hacks can be used without hex editors unlike some of the older hacks. Newer hacks, like "漢堡加蛋" (lit. hamburger w/ egg) introduced new functions like bundled in login functions.
In about 2007 quarter four, two gun hacking programs named Revolution Engine (SHAK) and DAEngine were developed. Players could obtain GASH-only equipment by using these hacking programs; however, the programs were more difficult to use in comparison to the past ones, so not too many players used them. The nProtect system was then updated and prevented these hacking programs from being used in the Hong Kong version of Heat Project. However, the unknown developers continue developing hacking programs.
Due to lack of moderating in the Hong Kong version, hacks are common in the server. Some people call Gamania as "爛橙" (rotten orange) due to bad service the inability to stop hacking, but Gamania has started to ban players, and change to a better anti-hack system, nProtect GameGuard to block hacking.
Despite using the GameGuard system, hacking is still possible. For example, in the Taiwan version, hackers used a fake GameGuard server to continue editing in-game items.
There are 4 localized versions released for now.
- Korea - Published by ParanGAME.
- Taiwan - Published by Gamania (遊戲橘子)
- Hong Kong - Published by Gamania (遊戲橘子)
- Mainland China - Published by Asia Eastern
- ↑ Heat Project - 武器裝備 (Weapons and Equipment)
- ↑ Heat Project - 階級說明 (Rank Description)
- ↑ Heat Project - 角色設定 (Setting your character)
- ↑ Heat Project - 遊戲操作說明 (Game Instruction)
- ↑ Heat Project - Game Characteristics
- ↑ 完全版 捉蟲皇后 2006 11 03 (download link of the "捉蟲皇后" hack")
- ↑ Heat Project - 玩家非法複製game points懲處(第二批處理名單)公告 (2nd list of banned players)
- ↑ Heat Project - 關於官方處理Heat Project外掛現況 (About how the administrators handle the hacking problem in the game)