This short article is in need of work. You can help Sega Retro by adding to it.
Thunder Force IV (サンダーフォースIV), called Lightening Force: Quest for the Darkstar in the US, is a 1992 shoot-'em-up by Tecnosoft released for the Sega Mega Drive. It is the fourth game in the Thunder Force series.
Shortly after defeating the ORN Empire in Thunder Force III, the Galaxy Federation comes under attack by survivors of the empire, who have banded together to form a new threat, Vios. Vios turns out to be more powerful than ORN ever was, and the Galaxy Federation must again use a new small craft to destroy their base on the planet Aceria.
Gameplay is almost identical to III: shoots (you have rapidfire), changes speed by 25% while holding the button down constantly adds 1%, changes weapon, and powerups are collected from enemies. Unlike III, however, you are not fixed to the camera motion; holding and will take you higher/lower than the screen limits (as in II).
Blade: Update of the standard shot. Destructive but big bullets, sometimes too big (see Strite boss)
Railgun: Update of the rear shot
Freeway: Small rockets that fire in the opposite direction of the ships movement
Snake: Bombs that travel along the ground/ceiling
Hunter: Homing orbs
The first four stages can be played in any order; the order listed here is the default.
A world full of clouds, mountains, and waters. You spend two "days" on this planet, primarily shooting down basic enemies that either just attack, shoot homing missiles at you, or worse. A giant serpent-like creature will come at you several times. A train-like underwater being will send smaller enemies hurling at you while trying to hit you with a large laser, and the rising boss ship will make it easier for homing missiles to hit you...
Boss: A giant ship with a fin on the bottom that shoots fireballs at you. Hit it enough and it will detach from the ship, revealing a free-moving sub-ship that will attack you in a variety of ways. Due to collision detection on the boss' weak spot, it's very difficult to damage him with the "Blade" weapon.
A blue ruin facing the void of space. Here you face larger robots on pedestals that are hard to defeat, pairs of laser-shooting shark-like beings, barriers that form as you move, and small, immobile enemies that generate themselves int he least convenient places. Halfway though you fight a giant robot that spams loads of bullets at you at once.
Possibly better called an outer space raid: you fly through an asteroid belt, avoiding the (multiple) turrets that constantly send bullets your way and follow your every move. You also have to dodge the regular enemies (they come fast) and avoid crashing into an asteroid. Halfway through, the astroids start moving at very high speeds, so pay attention to survive!
Fly through a desert sandstorm. Some enemies can take massive damage before going down.
Battle the boss ship from stage one in space
Water and Ice themed world, with the path over and under water being almost completely different play experiences
Lava themed world with a cameo boss
A stage in a bio-mechanic environment which consists mainly of miniboss fights
Last "proper" stage with moving walls and traps
Tips and tricks
The game has at least two score exploit points. The first is at the enemy just before going underwater in Strite. I constantly releases small enemies. The second is in the final stage, Versus. Keep playing until you reach the large cannon, which you normally must destroy to proceed. Power up items and 1UPs will keep respawning forever. Whether this was by design or an oversight is not clear.