The game controls uses 2 or 3 buttons used depending on the selected shuttle mode. The ship's armaments consist of air-to-air laser shots, air-to-ground missiles and any Power Weapons the player collects. The laser and missiles can be upgraded up to four times by collecting the powerups from drones that are shot. Power Weapons are available after the player collects three pieces of the same armour type or can be bought with credits acquired after each stage.
The weapons have limited power indicated on an energy meter. Using the weapons or getting the ship damaged lowers the energy. The energy can be recharged by collecting E power ups. Once the energy expires, the ship returns to normal mode. Depending on which mode is selected varies whether Button C or B activates the Power Weapons. Various hidden items can do certain things like an R item can put the shuttle in Reverse for a certain distance. The shuttle is destroyed by one shot or by running into an enemy unit or hazard. Unless the player collects enough K power-ups beforehand, the missiles and laser shots will be lost to minimum power when the player loses a life.
There are seven stages in the game, with the last one consisting of a single boss battle. The player has to fight through them avoiding hazards in addition. Mid-bosses occasionally appear in the game. When the player meets a mid-boss or end stage boss, the player must destroy weak points and various parts of the boss to destroy it.
Also known as ASO II: Last Guardian (Japanese: ASO II:ラスト ガーディアン, Hepburn: ASO II: Rasuto Gādian) in Japan. /wiki/Japanese_language
"VG - ASO II:ラストガーディアン". Beep! Mega Drive (in Japanese). No. 17. SoftBank Creative. February 1991. p. 130. https://retrocdn.net/index.php?title=File:BeepMD_JP_1991-02.pdf&page=132
"Oh! Neo Geo Vol. 7 - ASO II". Beep! Mega Drive (in Japanese). No. 42. SoftBank Creative. March 1993. p. 126. https://retrocdn.net/index.php?title=File%3ABeepMD_JP_1993-03.pdf&page=128
"Neo•Geo CD: The Arcade In A Box - Alpha Mission II". GamePro. No. Premiere Supplement. IDG. Spring 1996. p. 104. https://archive.org/stream/GamePro_The_Cutting_Edge_Spring_1996#page/n109/mode/2up
"VG - ASO II:ラストガーディアン". Beep! Mega Drive (in Japanese). No. 21. SoftBank Creative. June 1991. pp. 128–129. https://retrocdn.net/index.php?title=File:BeepMD_JP_1991-06.pdf&page=130
Alpha Mission II user's manual (Neo Geo AES, US)
Biondich, Paul (1998). "Alpha Mission II (Arcade) - Review". AllGame. All Media Network. Archived from the original on 14 November 2014. Retrieved 2019-07-21. http://allgame.com/game.php?id=9487&tab=review
Knight, Kyle (1998). "Alpha Mission II (Neo Geo Advanced Entertainment System) - Review". AllGame. All Media Network. Archived from the original on 15 November 2014. Retrieved 2019-07-21. http://www.allgame.com/game.php?id=16986&tab=review
Rand, Paul (October 1991). "Reviews - Neo Geo -- Alpha Mission II". Computer and Video Games. No. 119. Future Publishing. p. 61. https://archive.org/stream/computer-video-games-magazine-119/CVG119_Oct_1991#page/n60/mode/1up
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Demoly, Jean-Marc (November 1991). "Tests - Neo Geo - Alpha Mission II". Joystick (in French). No. 21. Sipress. p. 133. https://archive.org/stream/joystick021#page/n132/mode/1up
McFerran, Damien (April 7, 2017). "Alpha Mission II Review (Switch eShop / Neo Geo)". Nintendo Life. Nlife Media. Archived from the original on 2021-01-06. Retrieved 2019-07-21. http://www.nintendolife.com/reviews/switch-eshop/alpha_mission_ii_neogeo
Gibson, Casey (May 9, 2017). "Alpha Mission II (Switch) Review". Nintendo World Report. NINWR, LLC. Archived from the original on 2021-01-06. Retrieved 2019-07-21. http://www.nintendoworldreport.com/review/44598/alpha-mission-ii-switch-review
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"Reportaje - Clásicos en CD -- Titulos disponibles para el nuevo formato de SNK: Alpha Mission II". Hobby Hi-Tech (in Spanish). No. 1. Hobby Press. March 1995. p. 28. https://archive.org/stream/HiTechMagazine/HiTech%2001#page/n27/mode/1up
"NF編集部にまる - ネオジオゲームㇱインレビュー: ASO II~ラスト ガーディアン~". Neo Geo Freak (in Japanese). No. 25. Geibunsha. June 1997. pp. 124–128. https://archive.org/stream/neogeofreak0025#page/n127/mode/1up
Biondich, Paul (1998). "Alpha Mission II (Arcade) - Review". AllGame. All Media Network. Archived from the original on 14 November 2014. Retrieved 2019-07-21. http://allgame.com/game.php?id=9487&tab=review
Knight, Kyle (1998). "Alpha Mission II (Neo Geo Advanced Entertainment System) - Review". AllGame. All Media Network. Archived from the original on 15 November 2014. Retrieved 2019-07-21. http://www.allgame.com/game.php?id=16986&tab=review
Rand, Paul (October 1991). "Reviews - Neo Geo -- Alpha Mission II". Computer and Video Games. No. 119. Future Publishing. p. 61. https://archive.org/stream/computer-video-games-magazine-119/CVG119_Oct_1991#page/n60/mode/1up
Halverson, Dave; Off, Gregory; Stratton, Tom; Cockburn, Andrew (January 1993). "Viewpoint - Neo Geo - Alpha Mission 2". GameFan. Vol. 1, no. 3. DieHard Gamers Club. p. 13. /wiki/Dave_Halverson
Seb; Demoly, Jean-Marc (November 1991). "Test - Neo Geo - Alpha Mission II". Joypad (in French). No. 2. Yellow Media. pp. 126–127. Archived from the original on 2017-09-17. Retrieved 2021-01-06. https://www.abandonware-magazines.org/affiche_mag.php?mag=84&num=1771&album=oui
Demoly, Jean-Marc (November 1991). "Tests - Neo Geo - Alpha Mission II". Joystick (in French). No. 21. Sipress. p. 133. https://archive.org/stream/joystick021#page/n132/mode/1up
Drevet, Cyril (November 1991). "Dossier: La NÉO GÉO brille de tous ses feux - Alpha Mission II". Player One (in French). No. 14. Média Système Édition. p. 93. https://archive.org/stream/playerone-magazine-014c#page/n92/mode/1up
Cook, John (August 1991). "Coin Ops: Neo-Geo News". Sinclair User. No. 113. EMAP. p. 43. https://archive.org/stream/sinclair-user-magazine-114/SinclairUser_114_Aug_1991#page/n42/mode/1up
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Rosa, Piemarco (December 1992). "Alpha Mission II (Neo Geo)". Consolemania (in Italian). No. 14. Xenia Edizioni. pp. 54–55. https://archive.org/stream/Consolemania-014#page/n53/mode/2up
Wilson, David (November 1991). "Kill Zone - Alpha Mission II". Game Zone. Vol. 1, no. 1. Dennis Publishing. p. 82. https://archive.org/stream/game-zone-01#page/82/mode/1up
Stokes, Doris (November 1991). "Dosh Eaters: Alpha Mission II". Zero. No. 25. Dennis Publishing. p. 85. https://archive.org/stream/zero-magazine-25#page/n84/mode/1up
McFerran, Damien (April 7, 2017). "Alpha Mission II Review (Switch eShop / Neo Geo)". Nintendo Life. Nlife Media. Archived from the original on 2021-01-06. Retrieved 2019-07-21. http://www.nintendolife.com/reviews/switch-eshop/alpha_mission_ii_neogeo
Gibson, Casey (May 9, 2017). "Alpha Mission II (Switch) Review". Nintendo World Report. NINWR, LLC. Archived from the original on 2021-01-06. Retrieved 2019-07-21. http://www.nintendoworldreport.com/review/44598/alpha-mission-ii-switch-review
Daugherty, Kaelyn (June 19, 2017). "Review: ACA NEOGEO ALPHA MISSION II (Nintendo Switch)". Pure Nintendo Magazine. Pure Media, LLC. Archived from the original on 2021-01-06. Retrieved 2020-05-22. https://purenintendo.com/review-alpha-mission-2/