Sentinel is an interactive audio tower defense game. It mixes strategic gameplay with a dynamic music system.
User reviews: Mixed (49 reviews)
Release Date: Apr 22, 2014
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Recommended By Curators

"Fantastic soundtrack wrapped in a visualizing and challenging tower defense coat that is incredibly challenging and more of a puzzle than usual TD fare."
Read the full review here.


“If you’re quite fond of the tower defense genre, then you’d certainly be wise to add Sentinel to your play list.”

About This Game

Sentinel is an interactive audio tower defense game. It mixes strategic game play with a dynamic music system.

The game takes place on a sequencer-like grid. As you add defenses, collect resources and destroy enemies, musical elements are triggered in time to the music.

Fight through 31 levels to clear the virus from the system.

System Requirements

Mac OS X
SteamOS + Linux
    • OS: Windows XP or later
    • Processor: 2.0Ghz+
    • Memory: 2 GB RAM
    • Graphics: Shader Model 2.0+
    • Hard Drive: 750 MB available space
    • Additional Notes: Widescreen monitor required.
    • OS: OSX 10.5 or later
    • Processor: 2.0Ghz+
    • Memory: 2 GB RAM
    • Graphics: Shader Model 2.0+
    • Hard Drive: 750 MB available space
    • Additional Notes: Widescreen monitor required.
    • OS: Ubuntu 10.04 or later
    • Processor: 2.0Ghz+
    • Memory: 2 GB RAM
    • Graphics: Shader Model 2.0+
    • Hard Drive: 750 MB available space
    • Additional Notes: Widescreen monitor required.
Helpful customer reviews
20 of 22 people (91%) found this review helpful
1 person found this review funny
0.9 hrs on record
Posted: March 16
The emphasis on needing to get “perfect” levels killed the game when I reached the first gate. I cannot do it on any level. There is no “easy” mode or anything. You just have to get an absolutely perfect level to progress. Apparently this idea multiplies throughout the game for the rest of the checkpoints.

Mr. Brown, why not just have a simple progression system and just give an achievement for the perfectionists? The whole game is locked down basically :/

Like others have said, lots of mirco-managing, flashing colors, etc, but I didn’t mind any of it – pretty fun game for me and the micro-manage craziness actually had appeal… for the first 5 levels… till I got stuck… by needing at least one to be perfect. ^_^

Because of the craziness of switching your power back and forth from tower to tower, collecting money that’s falling, and using the manual tower, lots of things are happening very quickly – so to expect everybody who plays the game to be able to do that perfectly is a bit.. lame.

I never go for “100%s” or “max levels” or “all gold times” in games, I just like progressing casually. This is not possible in this game, you must be perfect... while you pay attention to 10 things at the same time.
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5 of 7 people (71%) found this review helpful
4.8 hrs on record
Posted: April 27
tl;dr -> Never has a tower-defence (TD) game made me rage so much at trying to 100% each level. 11/10 get my electronic groove fix.

I got this game gifted to me by a generous friend, and was very excited to try it because of the music, artstyle, and effects. I was extremely pleased with my experience.

If you like tower-defence games, managing multiple tasks rapidly (this is very, very important), electronic music, and fancy effects, then you will really like this game.

The aesthetics are very nice - the colors and backgrounds are alive with vivid color. The music is one of the most important elements in this game, and the tracklist is composed of very good electronic music. I strongly suggest you take a look at the trailer provided to get a feel for the music, or even search for the soundtrack on YouTube - the genre may not be to your liking. That being said, I absolutely love electronic dance music (EDM) and most subgenres related to it, so be aware of my personal bias in this regard. Note, the tracklist is more groovy, chillout electronic than the intense type typically played in clubs and on the radio - so don't expect buildups and drops.

I found the music to be wonderfully fit for creating a fun atmosphere despite that many times contrasts with how much task-switching you have to do during gameplay. As the beat progresses, a light flashes left-to-right across the level/background. If you have activated turrets, they will flash when the light passes over it, and the more turrets you have activated, the deeper/fuller/louder the music sounds. You will notice that the music will dull down whenever you have no powered turrets. The dynamic music (interacting with your turret placement) is done very well and has no effect on gameplay besides aesthetics.

The controls are simple - everything is done with the mouse - however, managing your actions/tasks is the most difficult part of the game. There is a very quick and helpful tutorial that begins right you start a new game, and the opening sequence is great. The learning curve is minimal to moderate depending on your familiarity with tower-defence games, but be warned - the game involves a lot of task-switching, so quick reflexes are essential if you want to avoid getting overwhelmed.

Gameplay involves you defending your core against waves of enemy viruses coming from different paths (numbered 1-x). There is a tracker that shows you what creeps are incoming, however, there is no real way of knowing what each virus does until you encounter them (no tooltips, no virus encyclopaedia, etc) and see for yourself. There are a variety of towers to use, each with different strengths. For example, there is a quick-firing beam that removes enemy shields, a slowing program, and an anti-worm (these are yellow non-circular viruses) program. Whenever you place a program there is a cooldown timer before you can place that specific program again. To counter this, a (quite expensive) cooldown reset ability can be purchased (refreshes all towers; must be bought each time you want to use it). There is also a free "manual aim" tower that can be placed, and I strongly suggest you place these whenever they are available to maximize your combat potential. To use the "manual aim" programs, you must click on them, then click and hold anywhere within their attack area. After a certain number of attacks (indicated by a bar underneath the tower), the program will disappear.

As you play, resource pickups will periodically drop from the top of the screen to a random part of the level - you need to click these to obtain the resources. Enemies will also sometimes drop smaller pickups, which are used to either upgrade your programs (up to a level of 2) or buy special items from your core. For example, you can buy a mine for 1 upgrade point, which allows you to place one-shot proximity mines; for 2 upgrade points, you can unlock a power generator program that supplies you with one power.

You start each level with a set number of power points needed to activate your programs. Whenever you build a new program/tower, it comes powered with 1 bar. You can use the mouse wheel to divert power to and away from your programs, and this is something that gets crazy as you progress deeper into the game. For example, you may have one tower with max power near the beginning of an enemy path, but once the creeps all make it past your program, you quickly cycle all the power out of that tower and divert it to your other programs further down the pathway. You must make these decisions in real-time, and it can get chaotic when a large amount of enemies are bearing down on your core.

There are gated checkpoints in the game that require you to beat a certain number of levels before you can proceed further. There is an icon given to you whenever you complete a level, as well as a second icon for achieving 100% (no damage to your core). I love tower-defence games and play a lot of them, so I give you all a warning: this is one of the most infuriating games to try to 100% (not necessarily a bad thing). It just takes one creep making it past you to ruin your run. Worse so are the bonus levels.

Aside from the main levels are bonus levels - which are scenarios that require you to use certain strategies. For example, one bonus level that took me ages involves you using the "manual aim" towers to soften up waves of enemies so your towers can finish them off. The catch? You have to make sure you attack each enemy the correct amount because you are given no resources to build more towers. There is another bonus level that taught me how to take advantage of programs and power (sometimes it is better to just buy a cheap program to get the extra power point) - you start off only able to build power stations, and the only available spots are at the bottom of the screen. To beat this stage, you must build power stations at the bottom, cycle power off, and divert it to the programs already supplied to you.

Overall, the game is a great staple of the genre, and anyone interested in electronic music, TD games, and being challenged should definitely give this a try.

Highly recommend!

DJSF @DJSF's Rogue Reviews

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2 of 2 people (100%) found this review helpful
11.7 hrs on record
Posted: March 13
UPDATE: Review switched from positive to negative. You have to be super-fast at multitasking, plus a wizard in order to keep playing this game. Painstakingly difficult and fast-paced (with all the looking around and clicking around). Recommended for masochists. (Original review below):

The "Mixed" user reviews factor for this game at the time of my writing is spot-on. There are positives and negatives that leave me loving and hating the game at once. Positive: I love the art and music, and the game is a really unique and challenging tower defense. Negative: The game is hectic and unforgiving if you want a perfect score. There is a LOT of frantic multitasking.
Some excellent ideas but the game just feels too intense for me. However, I still play it and it's better than a lot of other tower defences I've tried online. So I've tilted it into the "recommended" column.
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4 of 6 people (67%) found this review helpful
0.2 hrs on record
Posted: June 23
This game SUUUUCCCKKKSSS. You play on a boring blue grid background where you place uninteresting little squares on a few different possible squares to kill squares and circles that come. No pathing for a TD game. There is very few things a TD game has to do right, and by having uninteresting enemies, bland similar towers, and a boring environment, there isn’t much to keep this interesting. The menu and UI are terrible and don’t seem to have a working or logical main menu. You can’t easily exit the game from the main screen, probably because too many people try to do it after playing this game. There is no story either. Then there is the terrible tacked on micromanagement aspect which takes away any possible enjoyment. Not only do you have to have to gather resources and use them to build towers, but even THEN they still won’t work. You have to spend each level turning power off certain towers that aren’t in use by clicking and mouse scrolling on them (not a very intuitive control scheme) and then click back on the tower you want to use and mouse wheel scroll up. This means you are constantly going between like 6-10 towers turning power on and off. When it happens they come from both sides, which is often, you then basically are screwed, as you can only have half effectiveness on each, then when they get through to the next towers you have to turn 2 different towers off, then turn the next two on, with the exact right amount of power, which you don’t know what that is and how effective it will be. See how that could be annoying to do continuously. There is no time to build and enjoy, you are just turning power on and off for basically 90% of the game. Management aspect doesn’t work in this TD, and just makes playing a chore. Add that terrible mechanic to the rest of the “meh” game, and you have a “stinker” as DP would say. 3.5/10.
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2 of 3 people (67%) found this review helpful
15.3 hrs on record
Posted: April 7
As far as Tower Defense games go, Sentinel is a work of art. It combines some of the best and simplistic elements and crafts them together to form one excellent and strategic game that is very fun to play in bursts.

Sentinel has the basic Tower Defense gameplay, defending against hordes of oncoming enemies (or "Viruses" in this case) each with different strengths and weaknesses. It's main feature that gives it it's individuality aside from it's futuristic digital theme is probably the power consumption mechanic. Without any units of power, your defenses can't function. For each defensive object ("Towers" or "Anti-Viruses" or whatever you want to call them) you have deployed on the grid, you are supplied with one additional unit of power on top of the amount you are provided with by default (this varies from level to level), each defense can use up to 5 units of power, 1 being the minimum amount required to be funcitonal, 2 units through to 5 units supplies the defense with a strength and / or range boost. It sounds a little bit complicated, but it's very easy to learn after a few minutes of play.
Managing power in Sentinel can be very difficult and requires a lot of micro-managing, particularly because more often than not you'll need to sacrifice one of your operational defenses in order to activate another one on the other side of the grid. This game actually requires you to think rather than blindly placing defenses all over the place, especially in the bonus levels, just another thing that makes Sentinel great.

One of the other things pushes the right buttons for me is the theme and art-style in Sentinel, as you can tell from the screenshots and trailer it has cyber and futuristic features which is already a selling point to me, but on top of that it also includes some rthym elements, meaning that the background music ties in well with the gameplay. Already a definite must-have for my collection.
It's simple and minimalistic menu interface and level selection themes are also really well made, the game is just very easy on the eyes and pleasant to look at.
The interface is very simple and user friendly, thus easy to understand and can be picked-up very quickly, things like the radar will be crucial to your efforts when you begin playing and have learned the strengths and weakneses of each enemy.

The game is however not without some flaws, it has a "Gate" system which requires you to complete levels to acquire credits (at least, that's what I call them) in order to pass through to the next stages, while I don't have a problem with this mechanic, it will likely feel grindy and tedious after a while as the basic level completion credits are not enough to pass through all of the gates, you have to acquire more credits by defeating those levels again without the core taking any damage at all from incoming enemies, much easier said than done on a number of levels. This isn't a problem for those of you that like a challenge, but it can slow down progressing through the game a fair bit as all it takes is one virus to slip through to the core to force you to restart the level once again.

So all in all, considering the fact that this is a game that I acquired in a cheap bundle, it's a bloody good one. If you're into Tower Defense or Strategy games, add this one to your collection, it's a very affordable and fun game to play for when you're in that "I have nothing to play" mood. Honestly, I just wish there were some more levels to play as for me it ended too soon.

Matthew Brown, please consider a Sentinel sequel or some DLC.
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