Altitude

Altitude is a two-dimensional aerial combat game developed by Erik Measure and Karl Sabo and released for PC, Mac OS X and Linux in May 2009. It became available on Steam in December of that year.

Players can choose from five different planes and battle opponents across 2D landscapes ranging from the expected to the bizarre. Players earn Experience Points as they play and unlock customization perks. Game modes include Free For All, Team Deathmatch, Team Base Destruction and Ball. In TBD, you must work with your team to use special bomb pickups to attack the enemy's base while defending your own. In Ball, you work with your team to deliver a ball to the enemy's goal while defending your own. It can be fired from your plane to pass it to friendlies (watch out for interceptions!) or shoot a goal, or you may fly into the goal while carrying it. Touchdown!

Tropes used in Altitude include:

Abnormal Ammo: Missiles and bullets ahoy, but also things like electromagnetic pulses and corrosive gas canisters.
Amazing Technicolor Battlefield: Some maps are zanier then others.
Big Bulky Bomb: The aforementioned bombs.
Bomb Whistle: Emitted by the big bombs in Team Base Destruction when deployed.
Catch a Falling Star: Averted, as there's no one to catch you if your plane stalls. However, spamming your afterburner will allow you to restart your engine... preferably before you hit the ground.
Character Customization: You can change the appearance of your plane as well as utilize a perk system a la Call of Duty, divided into red, green and blue for a total of three perks equipped at a given time. The red perks determine weapons loadout and are specific to each plane while green and blue are utilitarian and general to all planes.
Deadly Gas : A perk for the Loopy replaces the EMP with a gas canister launcher that creates a cloud of corrosive gasses where it detonates. Any enemy plane that flies through it will suffer damage over time.
Energy Weapon: The Miranda is all about these, though the Loopy's EMP counts.
Emergency Weapon: The Bomber's tailgun is this, since as you might have guessed it fires backwards. It packs a nasty punch but puts a severe drain on the energy meter. It can be replaced with a flak cannon via a perk.
EMP: The Loopy's default secondary weapon fires an EMP burst, which causes any plane it hits to move and turn more slowly.
Everything Fades: When a plane is shot down, it turns gray, visually separating it from the action. When it hits the ground the wreck disappears.
Fragile Speedster: The Loopy is small, speedy and extremely maneuverable, making it excellent for hunting down other planes. In fact, it's default weapon set is called "Tracker".
Frickin' Laser Beams: A perk for the Miranda replaces it's default charge cannon with a charged laser beam that will continue to damage enemy planes for as long as you can keep it on them. Either weapon only fires small pulses unless first charged.
Grenade Launcher: The Bomber's primary weapon. Due to the weapon's arc, it helps to aim above the plane you're trying to hit. Otherwise, just lob them into melees.
Healing Factor: One perk allows your plane to regenerate health when not afterburning.
Heal Thyself: In addition to health pickups, in Team Base Destruction you can land your plane on your base to get instant full repairs. Upside-down, if need be.
High Altitude Battle: But of course.
Hyper-Destructive Bouncing Ball: Of a sort. Its quite bouncy and certainly looks destructive what with the spikes, but it is the focus of the destruction in Ball mode rather then the actual inflicter of it.
Interface Screw: Several weapons in this game make your plane go screwy. The Loopy's EMP makes you sluggish, while the Explodet's concussive rockets and mines knock you away- often into a wall. If that wasn't enough, its alternate Thermobaric rockets actually do invert your controls briefly, which is never a good thing.
Laser Sight: Visible from your plane to where you are aiming when using mouse controls.
Macross Missile Massacre: The Loopy can put out enough missiles to take any enemy down blindingly quickly. A perk for the Bomber replaces it's tailgun with actual bombs, which of course can be dropped carpet-style on the heads of your enemies.
Malevolent Architecture: Stay away from anything that looks solid. However, a server option allows the enabling of "bouncy" walls, which as you might expect cause you to bounce off of them with minimal damage instead of going boom.
Mana Meter: Your power meter is used both for boosting and using weapons, so balance your energy use accordingly.
Mighty Glacier: The Explodet is the largest, slowest and most heavily armored plane. Use it with the heavy armor perk to make it even tougher. The Bomber probably also qualifies due to not being any faster. It is, however, far more maneuverable.
More Dakka: In deference to the other planes, the Biplane relies on ballistics, and a lot thereof. Its primary is the Bomber's tailgun except forward facing, while its secondary spits out a cone of bullets over a much shorter range. Both can be fired at once, and the cone gun can be replaced with the long range, high-damage flak cannon. The recoil of either gun is sufficient to keep the plane in the air. A favored tactic of Biplane players is to float themselves on a cushion of bullets while shredding anyone beneath them. Its core drawback is the large energy use of its weapons.
Nitro Boost: All planes save the Miranda are capable of using afterburners to increase their speed, giving off a visable flame in their wake. The Miranda instead teleports several inches in the direction it was facing. It can also teleport backwards with the right perk equipped. Spamming your afterburners is necessary to restart your plane following a stall.
Power-Up: Pickups include Health, homing missiles and two kinds of barriers: One can be dropped to deter pursuers or deny an area to them, while the other is projected in front of the plane and blocks incoming damage.
Rule of Fun: As in any arcade-ish flight game, if given a choice between fun and physics, Altitude will err to the side of fun.
Sentry Gun: In Team Base Destruction each base is protected by a set of nasty automated flak guns. They can be destroyed, however, and do not come back for the duration of the round.
Side View
Roboteching: The above homing missiles, as well as the Loopy's primary missile weapon. An alternate weapon perk gives it dual missile fire in exchange for reduced homing capability.
Smart Bomb: Though not in the actual trope sense. The Explodet's secondary mine layer drops floating mines in it's wake. They explode about a half minute later unless an enemy plane flies near one, at which point it will chase after that plane.
Space Battle: One map has combatants maneuvering through an Asteroid Thicket. Of course, its physics do not defer from other maps.
Squishy Wizard: The Miranda. It lacks the speed of the Loopy and the armor of the heavier planes, but is capable of teleportation and reversing direction instantly. It's default weapon is a chargable Energy Weapon.
Stuff Blowing Up: Thanks to the Bomber and the Explodet, the latter of which even has manually-detonated rockets so you can be sure something blows up.
Taking The Bomb: If all else fails, you can stop a bomb from hitting your base by flying into its path.