The author of the guide is Sync.
In games, or in CS2D in this case, skill refers to how good the individual gamer plays. Ranging from a beginning gamer to a highly competitive professional, skill is something which everyone has, they just all differ from each other. Everyone has his own play style, tactics, strategies, favorite weapons, flaws, etc, each making the overall skill of the player. A beginner does not have a lot of skill because he has not accumulated enough experience in the game, so he has to play the game for some time in order to gain experience and learn, thereby growing better skills. Some are very skillful in aiming or strafing/dodging bullets, while others can be very skillful in tactics, making good use of the map layout. Others are very skillful with particular weapons such as the AWP, and others can be very skillful in captaining a team. Some are good with shotguns, some are good in rushing, some can have a very good insight on what the enemy might be thinking, to counter-act accordingly, while others can be good in teamwork or staying together in order to create a stronger force. Everyone differs in skill, and the ultimate player is one which has enough experience in all these fields.
On first sight, one might think a 2D game requires less aiming skill than an FPS, but this assumption is very wrong. In an FPS game, damage is often random depending on what body part you shoot on, and often more realistic because you die by just a couple of bullets. In CS2D, this is not the case because it is top-down view. Weapon damage is all strict-and-set, it all comes down to whether you aim and dodge better than your enemy. To get the feel for aiming, it requires a lot of experience. Once you have skillfully mastered the art of aiming, it will be very rewarding since you will notice you kill enemies faster with losing less HP yourself. Aiming cannot be tough, it comes along as you gain experience and get the feeling for CS2D's mechanics. In general, a good player will keep his pointer aimed at the enemy's head (or behind him) while shooting until he dies. The better you aim, the quicker your enemy dies therefore losing less HP as your enemy is dead and cannot shoot back.
If one stands still in a firefight, he will not accomplish much and will just lose a lot of HP and die quick like a sitting duck. The solution to this is dodging or strafing, the act of moving away from your enemy's bullets while you still keep your pointer (while shooting) at your enemy. Unlike an FPS, in CS2D there is no recoil thus there is no reason to stay still while shooting at the enemy. In a classic 1v1 "skill" testing match, such as in an empty map like aim_fr33kz (which has no walls in order to train your dodging/strafing) the player with the best of both aiming and dodging skills will come out at the top. Keep moving left and right, diagonal, and simply stay unpredictable while focusing on your pointer and aim, as the enemy does the same with you. If both players are very skillful, this all happens in a matter of seconds. Always see what HP your enemy has left when you die, and ask yourself what you did wrong, what mistake you made, or what could be improved. Are you not unpredictable enough when dodging? Is your aim not good enough? Keep this all in mind and gain experience, and learn from your mistakes as you grow in these skill factors.
Unpredictability is key. Use walls and obstacles and keep moving, don't stand still. You want to kill your enemy but you don't want to lose alot of HP so his next teammate can kill you. It is quite the accomplishment to have great skill in aiming and dodging, but it is only the individual's skill, and there is much more to cover about skills: weapons, maps, teamwork, strategies, and tactics.
You are a terrorist or a counter-terrorist, with a team and an enemy team, on a map. What is your mission? What are your objectives? What are you suppose to do? Always keep this in mind, depending on what map you play.
Let's take the most popular standard map in CS2D: de_dust. The terrorists must blow up crates which contains important materials, one of the terrorists is given a bomb which he has to plant at one of the 2 bombspots after travelling to the location. After the bomb is planted, the terrorists must defend the bombspot. The counter-terrorists' mission is to halt the terrorists from planting the bomb, eliminating all of them. Should the bomb be planted, they must hurry to defuse the bomb of which obviously is guarded by the terrorists, which you (obviously) need to kill first if you wish to defuse the bomb. The counter-terrorists are able to purchase a defuse-kit in order to defuse the bomb quicker.
This should all be very obvious to you, but even very skilled players often forget the most simplest thing you're trying to achieve: the highest teamscore.
By winning rounds either by killing the whole enemy team, exploding the bomb, or defusing the bomb, your team gains a score. The highest team score is the leading team. This is where it all ends upon. In public, organized teams, mixed matches, clan wars, league matches, you fight for the highest team score in order to be the winner. As a T, it is more important to defend the bomb rather than having more care about your personal score, so if you got the chance, you can get the counter-terrorists to spend time chasing you, trying to kill you, and when they kill you, they have no more time left to defuse the bomb which declares that the terrorist team wins the round! Never hesitate to give your life if you know it will do your team better, if you act as a team, you have higher chances of winning. Don't be a person that only cares about his personal score/kills/deaths, even skilled players make this mistake sometimes. In public it is acceptable, as it is just that: public. But in organized matches, where your team must achieve more points then the other, do not be arrogant and think more about your personal score.
Another situation: you're a CT with low HP and the enemy has planted the bomb, do you selfishly stay away wanting to have a good score (not risking a death) or do you attempt to defuse the bomb? Always take the chance to defuse the bomb! If you're chasing a terrorist which is trying to make you waste time, even if you have low HP, attempt a rush to kill him and quickly defuse the bomb! Why? It is better to try to rush and kill the terrorist where-after he kills you, rather then retreating and not dying. In the latter case, you would of simply gave away your enemy team a point. In the first case, you could of always be lucky/skillful and kill the terrorist, where-after you could defuse the bomb and win the round. There are some exceptions to this situation, for example if you are extremely sure you cannot defuse the bomb because there are too many terrorists and you have low HP and an expensive gun, and low money. In that case, it's better to hide and preserve your weapons so you have a chance to win next round, rather than dying and having no money to buy something next round.
Team score is more important then kills/deaths. This all applies to other game modes aswell, such as hostage rescue, etc.
Often seen as a beginner/newbie tactic. Camping means staying in 1 spot for quite a time, with the motive of surprising/ambushing an enemy when he walks by. It is a good tactic to use in fog of war to defend a certain spot. If you camp, stand in spots where you think your enemy will not look at, so when they walk by, you will have a split-second advantage. Also listen closely to footsteps, as you can guess and random-shoot before they even appear on your screen. As a CT, you better know the map very well and find out good spots and areas to defend. As a T, always try to think as the enemy, and where would you be if you were a CT? Try to surprise your enemies if you're camping, don't be predictable, and don't let yourself be surprised by a camping enemy. Check all areas, but not so frantically that you turn your back on more important places.
Rushing means that one person or a group forcefully run as quick as they can through a certain position, such as bombspot "B" for the terrorists in de_dust. It can either end up devastating for the rushers, or devastating for the surprised enemies. Rush when the enemy least expects it, either alone or with your whole team, your enemy will be stunned by the overwhelming rush and will either get alot of deaths or retreat, giving your team a certain position which is of tactical importance. In other occasions, it is very bad to attempt a rush, because your enemy might be prepared for it and already standing in good positions to counter the rush, causing alot of deaths for your team. In fog of war, where people often assume both teams are "shift"walking to neglect the other team of hearing any sound from you, it can be wise to rush for once because the enemy will not expect it. Timing is important, you can also attempt to rush with your whole team in the middle of the round or when the round is almost over (you need to plant the bomb/kill all CTs before the timer runs out, or else the CTs win). As a CT, sound is VERY important because it tells you if the Ts are rushing, and if you have stereo or headset, you can hear where they are coming from. Against a rush, don't wait untill you see them on screen, shoot BEFORE they enter your screen so they will get caught offguard. You might even kill their whole team! As a T, don't frequently rush, do it in unpredictable situations where the CTs don't expect it.
Flanking refers to the act of attempting to attack your enemy from the side or back, having obvious devastating effects on the enemy because he has to fight from 2 sides, giving you the edge in combat. If both teams are in a stalemate in the middle of a firefight, 1 person or a squad of players can attempt to go from the side and attack the enemy from the back, ending in great loss for the enemy team. Flanking can always be countered by having all paths defended by teammembers. This is a very vital tactic, and requires good timing and good communication between the teammembers. Attacking from 2 sides is mostly more effective then attacking with your whole team from 1 side (a whole group is an easy grenade target, unless you overrun the enemy with the "Rush" tactic). If attacking a bombspot, try to communicate with your teammembers to time the attacks on all sides at the same time, for maximum effect. If defending a bombspot or a very important area, be sure to have all paths defended from flanking attempts! Skilled players will have a good sense of where the enemy might be, and when to attempt a flank to get them from the back unprepared. If you're a CT, and your only teammember who defended another place has just died, be careful because a terrorist can now flank you. Set your priorities right, and try to face 1 enemy at a time, not 2 or more. Retreat if neccesary, or just rush and try to kill an enemy infront of you before someone comes behind you, or vice-versa.
This refers to shooting at random locations beyond your screen in an attempt to hit/kill enemies before they even see you, and is often used by very skillfull players. Look at your radar, do you not see teammates at a certain area? Then shoot that direction! Did you hear footsteps to the left? Then spray your weapon that direction. Good sniper players can always have a sense of where the enemy is, but it requires knowing the map very good. There are occasions where an AWPer can kill someone from beyond his screen, do not immediatly shout in anger that he's a hacker, some people really have the feeling for this. Shoot when you are sure you will hit/kill someone from afar, or else the missing bullets will tell the enemies where you are, putting you in an disatvantage. If you have plenty of ammo left, it's OK to sprayshoot and randomshoot, but if you have low ammo, be conservative and just shoot if an enemy is on your screen.
You can throw these at where you are standing in order so your enemy cannot see you, or see what weapon you have (usefull if you don't want to show you have a sniper/shotgun). It can also be used as a distraction/bait by throwing it at a tactical area and move away, and when you see/hear enemy shooting in the smoke to check if someone's inside, you have the advantage because you know they are heading your way so you can act accordingly. As a T, you can also throw them at where the bomb is planted in order to give the CT's just a little bit of vagueness of where the bomb is. They will still be able to see the ticking red alarm on the bomb however. Players with very tactical minds can use the Smoke Grenades for a lo of creative reasons. Don't ALWAYS hide behind smokes and palm trees, because it will be predictable. Hide sometimes, and sometimes don't. This leaves your enemy in a state of guessing.
These are meant for fog of war. It covers 3x3 tiles wide and shows everything inside it, including players walking through the flare. After a long period the flare will vanish and the fog will reappear. It is a very tactical grenade, and in an important match in fog of war it should almost always be used, especially by CT' to defend paths to the bomb spot. You can throw it on a 3 wide-tile path entrance and hide behind a wall and wait until you see an enemy walking through the flare and ambush him, or you can throw it somewhere and leave the whole area alone (psychological tactic) so that any enemy behind the flare thinks you are waiting for him so he will leave that path alone. You can also throw it behind a corner to see if someone is there. A very surprising and nice tactic is to rush with your whole team through a flare, as the enemy will be surprised by 3 or more players rushing through a flare, and most of the times the place where the flare is, is only guarded by 1 player. Rushing through a flare is a very useful tactic if you are sure they are fake-guarding it or if there is only 1 enemy behind the flare. A Flare used in conjunction with a Smoke Grenade can cause funny effects for the enemy. They might think the smoke is trying to cover-up the flare so that the other team will rush through it, so it leaves your enemy guessing. Plan your throws accordingly, and do not stack flares on top of each other because that is just wasteful. If you picked up another Flare, wait for the previous thrown flare to cease out until you throw this one. That way, it will leave that spot un-fogged the entire round, which is useful as a CT. As a T, you can throw flares around corners to check if there is any camping CT, useful before you rush. You can also save your flares until your team takes a bombspot and plants the bomb, so you now take a defensive position and use the flares the same way CT's.
The M4A1 has better accuracy, but costs more. The AK47 is very cost-efficient, but has less accuracy. Despite traditional belief, the AK does NOT do more damage than the M4A1, they do equal damage in CS2D. It all depends on the player's taste. The AK47 might seem like a bulletspraying-beast, but since this is CS2D and not an FPS, the big recoil doesn't matter as much. The bad accuracy makes it so someone with bad aim can still hit because of the wide area it sprays bullets with. The M4A1 has good accuracy, this is very useful in FPS games where better accuracy means good aim, but since this is in 2D perspective the good accuracy means a less wide area the bullets will go into, making someone with bad aim not do much damage. However, a very skillful player with good aiming is able to use the M4A1's good accuracy to devastating effect, and able to kill enemies in a matter of seconds. The M4A1 is also better off in spraying those tiny corridors, but the AK47 is better off spraying in areas with wide open space where the bullets will certainly hit someone. The AK47 is also a lot cheaper, so it sometimes can still be bought in "economical money crisis" situations instead of Kevlar&helm/grenades.