What i have so far

#include "FastLED.h"

#define DATA_PIN 0
#define BUTTON_LEAD 4
#define NUMBER_OF_MODES 4
#define LED_TYPE WS2812B
#define COLOR_ORDER GRB
#define NUM_LEDS 175
CRGB leds[NUM_LEDS];


#define BRIGHTNESS 255
#define FRAMES_PER_SECOND 120

//The following constant is the delay between each pixel flash
const int interval = 25;
unsigned long previousMillis = millis();
int mode = 1; //Default mode is one.

bool buttonState = LOW;
bool lastButtonState = LOW;


void setup(){
  pinMode(BUTTON_LEAD, INPUT_PULLUP);
  FastLED.addLeds<LED_TYPE, DATA_PIN, COLOR_ORDER>(leds, NUM_LEDS).setCorrection(TypicalLEDStrip);
  FastLED.setBrightness(BRIGHTNESS);
}

uint8_t gHue = 0;

void loop() {

  switch (mode) {
    case 1:
      sinelon();
      break;

    case 2:
      confetti();
      break;

    case 3:
       juggle();
       break;

     case 4:
      bpm();
      break;

    default:
      mode = 1;
      break;
  }
  FastLED.show();
  EVERY_N_MILLISECONDS( 20 ) { gHue++; }
}

/* monitor button press */
bool buttonListener() {
  bool modeChanged = false;

  buttonState = digitalRead(BUTTON_LEAD);

  if (buttonState != lastButtonState) {
    if (buttonState == LOW) {
      mode++;
      modeChanged = true;
      delay(250);             // Debounce delay. I checked the best parameter and 250 was it.
    }
  }
  lastButtonState = buttonState;

  return modeChanged;
}

void sinelon() {
  if(buttonListener()) { return; }
  if(millis() - previousMillis >= interval) {
      previousMillis = millis();
  fadeToBlackBy(leds, NUM_LEDS, 20);
  int pos = beatsin16(13,0,NUM_LEDS);
  leds[pos] += CHSV(gHue, 255, 192);
}
}

void confetti() {
  if(buttonListener()) { return; }
  if(millis() - previousMillis >= interval) {
      previousMillis = millis();
  fadeToBlackBy(leds, NUM_LEDS, 10);
  int pos = random16(NUM_LEDS);
  leds[pos] += CHSV( gHue + random8(64), 200, 255);
}
}

void juggle() {
  if(buttonListener()) { return; }
  if(millis() - previousMillis >= interval) {
      previousMillis = millis();
  fadeToBlackBy(leds, NUM_LEDS, 20);
  byte dothue = 0;
  for(int i = 0; i < 8; i++) {
    leds[beatsin16(i+7,0,NUM_LEDS)] |= CHSV(dothue, 200, 255);
    dothue += 32;
  }
}
}

void bpm() {
  if(buttonListener()) { return; }
  if(millis() - previousMillis >= interval) {
      previousMillis = millis();
  uint8_t BeatsPerMinute = 62;
  CRGBPalette16 palette = PartyColors_p;
  uint8_t beat = beatsin8(BeatsPerMinute, 64, 255);
  for(int i = 0; i < NUM_LEDS; i++) {
    leds[i] = ColorFromPalette(palette, gHue+(i*2), beat-gHue+(i*10));
  }
}
}