Slap Fight



Slap Fight, also known as Alcon, is a vertically scrolling shoot-em-up developed by Toaplan and released in 1986. It is notable for its upgrade system similar to Gradius.

Gameplay Overview
Slap Fight is a typical game with 8-way movement, a shot button, and a secondary button to activate upgrades. Like most Toaplan titles, it features a checkpoint system, as well as the loss of all power ups after a death.

Controls

 * A: Shoots the equipped weapon
 * A (Hold): With Laser equipped, the ray will travel further. With other weapons, will fire automatically at a very slow rate.
 * B: Activates the upgrade highlighted in the bar

Upgrade Bar


The game features an upgrade bar similar to Gradius. By collecting stars, the player advances the upgrade bar, and can press the second button to activate the corresponding upgrade. If the player collects a Star while the last upgrade is highlighted, the selection rolls back to the first upgrade again. If the player dies while one upgrade is highlighted, or pressed Up+Right+A+B upon respawning, they start their next life with the Speed already highlighted. Otherwise, the player resumes with no upgrade.

The Shot, Bomb, Laser and Homing Missiles are mutually exclusive, and activating one will deactivate the one that was active before.

Activating any shot type or the Wing power-up will move the ship close to the middle of the screen and award the player around 2 seconds of full invincibility. However, probably due to a glitch, activating another power-up while the invincibility timer is still running won't reload it. This means that, for an example assuming the timer is 2 seconds, if you activate an upgrade, then 1.5 seconds later upgrade again, you will only have 0.5 seconds of invincibility left instead of another 2 seconds.


 * Speed: Increases the ship's speed. Up to 5 Speed Ups can be stacked. There is no way to lower the ship's speed to a lower level without dying, aside from the small decrease when activating the first Wing upgrade.
 * Shot: Activates the starting shot again. Limited range, but can deal decent damage to every type of enemy.
 * Side: Activates a secondary weapon fired from each side of the ship. Can be stacked with any other weapon.
 * Wing: Can be stacked up to three times, increasing the firepower each time (and, for H. Missiles, the missiles' speed). The first upgrade will make the ship wider and a little slower, while the second and third upgrade will made two options appear each time, one on each side of the ship. Options can be destroyed by enemies, and the upgrade can be activated again after this happens. Whenever one option is destroyed, the one on the other side of the ship is also destroyed.
 * Bomb: Fairly powerful weapon, but with range similar to Shot, and terrible reload time.
 * Laser: Long-range weapon. The player has to keep the button pressed for the shot to hit long distances, otherwise the ray will disappear. It is inefficient against the rail and diamond enemies.
 * H. Mis: Will fire one homing missile for each enemy present on screen, with a few exceptions for some midbosses. If no targets are on screen, the ship will fire many missiles in all directions. Cannot be fired again until all missiles hit their targets or left the screen, but the Side secondary weapon will keep shooting normally. It is almost useless against the rotating turrets in the second half of the game.
 * Shield: Limited duration shield that can withstand a few hits. Getting hit will decrease the shield's timer.

General secrets

 * If the player died with no upgrade pending, it is possible to start the next life as if they collected one star by keeping Up+Right+A+B pressed. It is also possible to perform this trick at the start of a credit.


 * After starting a game, if the player dies without having scored any point, they will respawn with complete Wings and the homing missiles, as well as 1,000 points earned. However, no speed up will have been granted, nor the Side shot.




 * If the player reaches a certain point in the game without destroying anything, dying will award the player hundreds of thousands of points and will make them respawn much later in the game, and once again with complete Wings and the homing missiles. The longer the player survives, the more points are earned, and the further they will respawn. The earliest occurrence of this trick is if the player can reach the area in the left screenshot above (roughly). In this case, they will be awarded 150,000 points and respawn after the section with the crystal tubes, skipping the first third of the game. Surviving a little longer will award more points.
 * The maximum possible amount of points that are possible to get with this trick appears to be 240,000, and the point to reach is roughly the one depicted in the right screenshot. Any survival beyond this is superfluous. In fact, even if the player can somehow reach beyond the "warp" checkpoint without scoring any point (which is next to impossible in an actual run with no cheats or tools), they will be warped back even if they would otherwise be eligible to a later checkpoint.




 * There are two hidden 1-up locations, in the form of a ? item revealed by firing at it with Shot. However, shooting again before collecting the item will destroy the extend and award the player 3,000 points instead. The extends are always in the same general location, but their exact location differs with each run. The first 1-up is located at the end of the part with the enemies in the tubes. The exact location of the second 1-up in the desert seems very inconsistent, and the item sometimes doesn't seem to be present. More research about this item has to be conducted.


 * If the player reaches specific spots while having the Shot equipped, and a certain number of stars collected, a helper ship will come and help them. The helper can only shoot if the Shot is equipped. More research about the exact spawn conditions has to be conducted.

Scoring secrets

 * When starting the game while pressing Down+Left+B, the player will be awarded an extra 10,000 points as soon as they earn their first points. A sound can be heard at the start of the game if the command was successful. Note that this secret is also stackable with the points obtained from dying without killing anything, and the 10,000 points will be awarded upon respawn, in addition to the points from the other trick.




 * If the player has the Shot weapon equipped at specific spots, an enemy from Space Invaders will appear on screen. The player can earn points by shooting at it repeatedly. With a good autofire frequency, and by staying close to it all the time, it is possible to earn around 80k points from each, making them a very good source of score. Having options can greatly help connecting as many shots as possible.




 * Using the Bomb in some specific spots (mainly in the area after the second midboss) reveals some plants, earning 1,000 points for each. Some roofs can also be destroyed by bombs, earning the player a whopping 170 points. Because these bonuses are low and the bomb is bad, the player may want to neglect those.




 * The player can bloom flowers by repeatedly firing their Laser at them. It is possible to earn around 15,000 points per flower. Keeping the button pressed rather than using fast autofire is more efficient. The optimal rythm for points appears to be around 15 frames ON and 2 frames OFF, while being as close to the flower as possible.




 * In many areas of the game, some metallic things are revealed by shooting Homing Missiles, and give 1,000 points when doing so. Destroying them also awards 150 additional points.


 * The faster the final boss is killed, the more points are earned. With high autofire frequency and the helper ship, it is possible to earn up to 240,000 points.

Loops
The game loops infinitely, with enemy aggression and bullet speed increasing with each loop. However, enemy bullet speed will be reset to a low speed when loop % 8 is equal to 1 (loop 9, 17, 25...), resuming a new cycle of bullet speed increase.

As the game loops infinitely, scoring mainly comes from clearing several loops, but there are many scoring secrets to take into account in order to reduce the number of loops needed to reach certain score thresholds. A loop with optimized scoring can earn roughly twice as many points as a loop with no scoring effort. As such, it is possible to reach the counterstop (9,999,990 pts) after around 16 loops by scoring, which could take around 30 loops otherwise.