:root {

    /* Auth colours are those used in authentication pages (login/registration/password) */
    
    --auth-colour-bg-white: #ffffff;
    --auth-colour-bg-accent-1: #effcff;

    --auth-colour-link-hover: var(--colour-link-hover);
    --auth-colour-soft-purple: #eff3ff;
    --auth-colour-accent-soft: #e4f5e6;

    --colour-text-primary: #1F2937;
    --colour-text-secondary: #6B7280;
    --colour-text-strong: #003C13;
    --auth-colour-focus-ring: #a38eff;

    --auth-shadow-focus: 0 0 8px rgba(163, 142, 255, 0.4);
    --auth-shadow-focus-strong: 0 0 8px rgba(163, 142, 255, 0.6);
    --auth-shadow-cta: 0 0 8px rgba(220, 137, 234, 0.6);


    --form-input-border: #BFAEFF;
    --form-input-bg: #f7f4ff;
    --form-input-bg-hover: #e8e0ff;
    --form-input-bg-disabled: #f0ecf8;
    --form-input-border-disabled: #d1c4e9;

    /* Generic states */
    --state-danger: #B4233D;
    --state-danger-soft: #fff5f5;
    --state-success: #2F7A4E;
    --state-success-strong: #25633F;
    --state-success-soft: #f5fff5;

    --auth-colour-violet: #8702C0;
    --auth-colour-violet-dark: #29003c;

    /* CTA Gradients */
    --cta-start: #AA4AC2;
    --cta-end: #B02CD9;
    --cta-disabled-start: #b8a0d1;
    --cta-disabled-end: #8b1db5;
    --cta-alt-start: #8555CF;
    --cta-alt-end: #542cd9;

    --font-heading: "Poppins", Inter, Arial, sans-serif;
    --font-body: "Inter", Arial, sans-serif;

    --nav-height: 4.5rem;
}

html, body {
    margin: 0;
    padding: 0;
    background-color: var(--auth-colour-bg-accent-1);
    font-family: var(--font-body);
    height: 100%;
}

/* || Navigation */

nav {
    padding: 1.25rem 1.75rem;
    height: var(--nav-height);
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-sizing: border-box;
    box-shadow: var(--shadow-nav);
    z-index: 999;
    background-color: var(--auth-colour-bg-accent-1);
}

nav a {
    font-size: 1.25rem;
    font-weight: 600;
    text-decoration: none;
    color: var(--colour-text-primary);
    white-space: nowrap;
}

nav a#logo {
    text-align: left;
}

nav a#login-link {
    text-align: right;
}

/* || Form Layout */

#form {
    margin-top: var(--nav-height);
    width: 100%;
    display: flex;
    flex-direction: column;
    overflow-y: auto;
    scroll-behavior: smooth;
    scroll-snap-type: y mandatory;
    min-height: calc(100vh - var(--nav-height));
    box-sizing: border-box;
    padding: 0;

    /* Hide scrollbar*/
    scrollbar-width: thin;
    scrollbar-color: var(--colour-overlay-medium) transparent;
}

/* Hide scrollbar for Chrome, Safari, Edge */
#form::-webkit-scrollbar {
    width: 8px;
}

#form::-webkit-scrollbar-track {
    background: transparent;
}

#form::-webkit-scrollbar-thumb {
    background: var(--colour-overlay-medium);
    border-radius: 4px;
}

#form::-webkit-scrollbar-thumb:hover {
    background: var(--colour-overlay-strong);
}

#form section {
    min-height: calc(100vh - var(--nav-height));
    width: 100%;
    display: none;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    scroll-snap-align: start;
    scroll-snap-stop: always;
    box-sizing: border-box;
    padding: var(--gap-medium);
    gap: var(--gap-small);
}

#form section.active {
    display: flex;
}

#form h1 {
    margin: 0 0 var(--gap-small);
    text-align: center;
    font-family: var(--font-heading);
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--colour-text-primary);
    line-height: 1.2;
}

#form h2 {
    margin: 0 0 var(--gap-small);
    text-align: center;
    font-family: var(--font-heading);
    font-size: 2rem;
    font-weight: 600;
    color: var(--colour-text-strong);
    line-height: 1.3;
}

#form .form-body {
    width: 100%;
    flex: 1;
    display: flex;
    justify-content: center;
    align-items: center;
}

#form .form-elements {
    display: flex;
    flex-direction: column;
    align-items: center;
    width: 90%;
    max-width: 500px;
    gap: var(--gap-small);
}

#form .group-fields {
    display: flex;
    flex-direction: column;
    width: 100%;
    gap: var(--gap-small);
}

/* || Inputs */

#form input[type="text"],
#form input[type="email"],
#form input[type="password"],
#form select {
    width: 100%;
    padding: 0.875rem 1.5rem;
    font-size: 1.125rem;
    border: 2px solid var(--form-input-border);
    border-radius: 50px;
    background-color: var(--form-input-bg);
    color: var(--colour-text-strong);
    font-family: var(--font-body);
    transition: border-color 0.2s ease, background-color 0.2s ease, box-shadow 0.2s ease;
}

#form input[type="text"]:focus,
#form input[type="email"]:focus,
#form input[type="password"]:focus,
#form select:focus {
    outline: none;
    border-color: var(--auth-colour-focus-ring);
    background-color: var(--auth-colour-bg-white);
    box-shadow: var(--auth-shadow-focus);
}

#form input.error,
#form select.error {
    border-color: var(--state-danger);
    background-color: var(--state-danger-soft);
    animation: error-shake 0.4s;
}

#form input.success,
#form select.success {
    border-color: var(--state-success);
    background-color: var(--state-success-soft);
}

/* || Buttons */

#form button {
    font-family: var(--font-body);
    cursor: pointer;
    border: none;
    border-radius: 50px;
    transition: all 0.3s ease;
}

#form button:disabled {
    cursor: not-allowed;
    opacity: 0.6;
} 

#form button.next {
    padding: 0.95rem 2.6rem;
    font-size: 1.25rem;
    background: linear-gradient(145deg, var(--cta-start), var(--cta-end));
    color: var(--auth-colour-bg-white);
    font-weight: 700;
}

#form button.next:hover:not(:disabled) {
    filter: brightness(0.95);
    box-shadow: var(--auth-shadow-cta);
}

#form button.next:disabled {
    box-shadow: none;
    background: linear-gradient(145deg, var(--cta-disabled-start), var(--cta-disabled-end));
    transform: scale(0.98);
}

#form button.option {
    padding: 0.85rem 1.75rem;
    font-size: 1.05rem;
    border: 2px solid var(--form-input-border);
    background: var(--form-input-bg);
    color: var(--auth-colour-violet);
    font-weight: 600;
}

#form button.option:hover {
    background: var(--form-input-bg-hover);
    border-color: var(--auth-colour-focus-ring);
}

#form button.option:disabled {
    border-color: var(--form-input-border-disabled);
    background: var(--form-input-bg-disabled);
    color: var(--colour-text-secondary);
    transform: scale(0.98);
}

/* || Text Elements */

#form .subtitle {
    margin-bottom: var(--gap-small);
    text-align: center;
    font-size: 1.125rem;
    font-weight: 500;
    color: var(--colour-text-secondary);
    line-height: 1.5;
}

#form .subtitle a {
    color: var(--auth-colour-violet);
    text-decoration: none;
    font-weight: 600;
    transition: color 0.2s ease;
}

#form .subtitle a:hover {
    color: var(--auth-colour-link-hover);
    text-decoration: underline;
}

#form small {
    font-size: 1rem;
    color: var(--colour-text-secondary);
    text-align: center;
    line-height: 1.5;
    margin-top: 0.5rem;
}

/* || Responsive Breakpoints */

@media (max-width: 900px) {
    nav {
        padding: 1rem 1.25rem;
        gap: 1rem;
    }

    nav a {
        font-size: 1.1rem;
    }
}

@media (max-width: 768px) {
    html, body {
        overflow-y: auto;
    }

    #form {
        scroll-snap-type: none;
        min-height: auto;
    }

    #form section {
        min-height: auto;
        padding: var(--gap-small) var(--gap-xsmall);
        scroll-snap-align: none;
        scroll-snap-stop: normal;
    }

    #form h1 {
        font-size: 2rem;
    }

    #form h2 {
        font-size: 1.6rem;
    }

    #form .form-elements {
        width: 100%;
        max-width: 100%;
    }

    #form input[type="text"],
    #form input[type="email"],
    #form input[type="password"],
    #form select {
        font-size: 1rem;
        padding: 0.75rem 1.1rem;
    }

    #form button.next,
    #form button.option {
        width: 100%;
    }

    #form .presubmit-options {
        flex-direction: column;
        align-items: stretch;
    }

    #form .presubmit-options button {
        max-width: none;
    }
}

@media (max-width: 480px) {
    nav a {
        font-size: 1rem;
    }

    #form h1 {
        font-size: 1.8rem;
    }

    #form .subtitle,
    #form small {
        font-size: 0.95rem;
    }
}

/* || Animations */

@keyframes error-shake {
    0% { transform: translateX(0) rotate(0deg); }
    15% { transform: translateX(-6px) rotate(-3deg); }
    30% { transform: translateX(6px) rotate(3deg); }
    45% { transform: translateX(-6px) rotate(-2deg); }
    60% { transform: translateX(6px) rotate(2deg); }
    75% { transform: translateX(-3px) rotate(-1deg); }
    100% { transform: translateX(0) rotate(0deg); }
}