@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&display=swap');

:root {
    /* Color Palette */
    --primary-color: #3b82f6;
    --primary-gradient: linear-gradient(135deg, #60a5fa, #3b82f6);
    --primary-hover: #2563eb;
    --background-color: #f8f9fa;
    --card-background: #ffffff;
    --text-main: #1f2937;
    --text-secondary: #4b5563;
    --success-color: #10b981;
    --error-color: #ef4444;
    --fsrs-good-color: #41b8eb;
    --fsrs-good-hover: #2fa0cf;

    /* Spacing & Layout */
    --border-radius-lg: 24px;
    --border-radius-md: 16px;
    --border-radius-sm: 12px;
    --border-radius-pill: 50px;
    --top-menu-height: 70px;

    /* Effects */
    --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --shadow-glow: 0 0 15px rgba(59, 130, 246, 0.5);

    /* Transitions */
    --transition-fast: 0.2s ease;
    --transition-medium: 0.3s ease;
}

body {
    margin: 0;
    font-family: 'Inter', sans-serif;
    background-color: var(--background-color);
    color: var(--text-main);
    min-height: 100dvh;
    display: flex;
    flex-direction: column;
    justify-content: flex-start;
    align-items: center;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

#app {
    display: flex;
    flex-direction: column;
    width: 100%;
    max-width: 600px;
    /* Mobile-first constraint */
    flex: 1;
    min-height: 100dvh;
    padding: 16px 16px 0;
    box-sizing: border-box;
}

#app.page-centered {
    justify-content: center;
    align-items: center;
    padding-bottom: 20px;
}

/* --- Top Menu --- */
#top-menu {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px 0;
    margin-bottom: 8px;
    width: 100%;
    min-height: calc(var(--top-menu-height) - 10px);
}

#add-btn a {
    display: flex;
    justify-content: center;
    align-items: center;
    width: 50px;
    height: 50px;
    background: var(--fsrs-good-color);
    color: #ffffff;
    border-radius: 50%;
    text-decoration: none;
    font-size: 34px;
    font-weight: 600;
    box-shadow: var(--shadow-sm);
    transition: var(--transition-fast);
}

#add-btn a:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
    background: var(--fsrs-good-hover);
}

#top-menu p {
    margin: 0;
    font-size: 0.9rem;
    color: var(--text-secondary);
    font-weight: 500;
    background: var(--card-background);
    padding: 18px;
    border-radius: var(--border-radius-pill);
    box-shadow: var(--shadow-sm);
}

/* --- Card Container --- */
#card {
    flex: 1;
    display: flex;
    flex-direction: column;
    justify-content: flex-start;
    align-items: stretch;
    width: 100%;
    height: calc(100dvh - var(--top-menu-height) - 38px);
    padding-bottom: 12px;
    perspective: 1000px;
    /* For potential 3D flips later */
}

.card {
    background-color: var(--card-background);
    color: var(--text-main);
    border-radius: var(--border-radius-lg);
    padding: 32px 24px;
    box-sizing: border-box;
    width: 100%;
    min-height: 300px;
    flex: 1;
    height: calc(100% - 15px);
    display: flex;
    flex-direction: column;
    justify-content: flex-start;
    align-items: stretch;
    gap: 18px;
    text-align: center;
    box-shadow: var(--shadow-lg);
    border: 1px solid rgba(255, 255, 255, 0.5);
    /* Subtle border */
    position: relative;
    transition: transform var(--transition-medium);
}

.card.card--answer-mode {
    padding-top: 20px;
    padding-bottom: 24px;
    gap: 12px;
}

/* --- Audio question layout --- */

.card.card--audio-question #bottom-area {
    margin-top: auto;
    display: flex;
    flex-direction: column;
    align-items: stretch;
    gap: 10px;
}

.card.card--audio-question #buttons {
    margin-bottom: 12px;
}

.card.card--audio-question #audio {
    margin-bottom: 8px;
}

.card.card--audio-question.card--answer-mode #audio {
    margin-bottom: auto;
}

.card.card--audio-question.card--answer-mode #bottom-area {
    min-height: 140px;
}

.card--form {
    flex: initial;
    height: auto;
    min-height: initial;
    justify-content: center;
    align-items: center;
    gap: 30px;
}

.card--form form {
    width: 100%;
}

#question {
    font-size: 1.75rem;
    font-weight: 700;
    line-height: 1.4;
    margin-bottom: 14px;
}

#answer {
    font-size: 1.5rem;
    color: var(--text-secondary);
    margin-top: 12px;
    padding: 16px;
    /* background: rgba(243, 244, 246, 0.5); */
    border-radius: var(--border-radius-md);
    width: 100%;
    box-sizing: border-box;
    text-align: center;
    animation: fadeIn 0.5s ease-out;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 8px;
}

#answer p {
    margin: 0;
    width: 100%;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* --- Audio --- */
#audio {
    width: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 12px;
}

audio {
    width: 100%;
    border-radius: var(--border-radius-pill);
    box-shadow: var(--shadow-sm);
}

/* --- Bottom area wrapper (audio + buttons) --- */
#bottom-area {
    display: flex;
    flex-direction: column;
    align-items: stretch;
    gap: 10px;
    margin-top: auto;
}

/* --- Buttons --- */
#buttons {
    width: 100%;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 18px;
    margin-top: auto;
    margin-bottom: 25px;
}

#buttons.answer-mode {
    display: flex;
    flex-direction: column;
    align-items: stretch;
    gap: 12px;
    margin-top: 8px;
}

button {
    border: none;
    color: white;
    text-align: center;
    text-decoration: none;
    display: inline-flex;
    justify-content: center;
    align-items: center;
    font-size: 1.1rem;
    font-weight: 600;
    padding: 16px 32px;
    border-radius: var(--border-radius-pill);
    cursor: pointer;
    width: min(280px, 100%);
    margin: 0 auto;
    transition: all var(--transition-fast);
    box-shadow: var(--shadow-md);
    letter-spacing: 0.5px;
}

#buttons.answer-mode button {
    max-width: none;
    width: 100%;
}

.btn-label {
    font-size: 1.3rem;
    font-weight: 700;
}

.next {
    font-size: 0.9rem;
    font-weight: 500;
    margin-left: 12px;
    opacity: 0.9;
    padding-top: 4px;
    /* Slight alignment adjustment */
}

.save-btn {
    margin-bottom: 10px;
}

.blue-btn {
    background: var(--fsrs-good-color);
    color: #ffffff;
}

.blue-btn:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
    background: var(--fsrs-good-hover);
}

.blue-btn:active {
    transform: translateY(0);
}

/* --- Play Button Customization --- */
#play-btn {
    background: var(--card-background);
    border-radius: 50%;
    padding: 4px;
    margin: 4px;
    border: 2px solid var(--fsrs-good-color);
    color: var(--fsrs-good-color);
    transition: all var(--transition-fast);
    width: 60px;
    height: 60px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    box-shadow: var(--shadow-sm);
}

#play-btn:hover {
    background: var(--fsrs-good-color);
    color: #ffffff;
    transform: scale(1.1);
    box-shadow: var(--shadow-md);
}

#play-btn.pressed {
    transform: scale(0.95);
    background: var(--fsrs-good-hover);
    border-color: var(--fsrs-good-hover);
    color: #ffffff;
}

/* --- Forms & Inputs --- */
.form-group {
    margin-bottom: 1.5rem;
    width: 100%;
}

.form-control {
    width: 100%;
    padding: 12px 16px;
    font-size: 1rem;
    border: 2px solid #e5e7eb;
    border-radius: var(--border-radius-sm);
    transition: border-color var(--transition-fast);
    box-sizing: border-box;
    font-family: 'Inter', sans-serif;
}

.form-control:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

/* --- Utilities --- */
.edit-icon {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    margin-left: 10px;
    text-decoration: none;
    font-size: 1.2rem;
    opacity: 0.5;
    transition: opacity var(--transition-fast);
}

.edit-icon:hover {
    opacity: 1;
}

.spinner {
    display: block;
    width: 50px;
    height: 50px;
    border: 4px solid rgba(59, 130, 246, 0.1);
    border-radius: 50%;
    border-top-color: var(--primary-color);
    animation: spin 1s linear infinite;
    margin: 24px auto 0;
    align-self: center;
}

@keyframes spin {
    0% {
        transform: rotate(0deg);
    }

    100% {
        transform: rotate(360deg);
    }
}

/* --- Toast --- */
.toast-message {
    position: fixed;
    top: 20px;
    right: 20px;
    background-color: var(--success-color);
    color: white;
    padding: 16px 24px;
    border-radius: var(--border-radius-md);
    box-shadow: var(--shadow-lg);
    display: none;
    z-index: 9999;
    font-weight: 500;
    font-size: 0.95rem;
    align-items: center;
    gap: 10px;
}

.toast-message.error {
    background-color: var(--error-color);
}

.toast-message.show {
    display: flex;
    animation: slideIn 0.3s cubic-bezier(0.68, -0.55, 0.265, 1.55);
}

@media (max-width: 420px),
(max-height: 720px) {
    #app {
        padding: 12px 12px 6px;
    }

    #top-menu {
        padding: 8px 0;
        min-height: calc(var(--top-menu-height) - 20px);
        margin-bottom: 0px;
    }

    #top-menu p {
        padding: 12px 16px;
        font-size: 0.82rem;
    }

    .card {
        padding: 24px 18px;
        min-height: 0;
        height: auto;
        gap: 16px;
    }

    #question {
        font-size: 1.35rem;
    }

    #answer {
        font-size: 1.2rem;
        padding: 16px;
    }

    button {
        font-size: 1rem;
        padding: 12px 18px;
    }

    #buttons {
        margin-bottom: 16px;
    }
}

@media (max-width: 600px) and (orientation: portrait) {
    body {
        background-color: #ffffff;
    }

    #app {
        padding: 0;
        background-color: #ffffff;
        min-height: 100dvh;
    }

    #top-menu {
        background-color: var(--card-background);
        padding: 12px 16px;
        margin: 0;
        box-shadow: none;
        box-sizing: border-box;
    }

    #add-btn a {
        box-shadow: 0 6px 16px rgba(59, 130, 246, 0.25);
    }

    #top-menu p {
        box-shadow: none;
    }

    #card {
        padding: 0;
        height: auto;
    }

    .card {
        border-radius: 0;
        box-shadow: none;
        border: none;
        min-height: 100%;
        height: auto;
        padding: 24px 16px 32px;
    }
}

@keyframes slideIn {
    from {
        transform: translateX(100%);
        opacity: 0;
    }

    to {
        transform: translateX(0);
        opacity: 1;
    }
}

/* --- Back Button --- */
#back-icon {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background: var(--fsrs-good-color);
    color: #ffffff;
    box-shadow: var(--shadow-sm);
    margin: 20px;
    transition: var(--transition-fast);
    border: 1px solid var(--fsrs-good-color);
}

#back-icon:hover {
    transform: translateX(-3px);
    box-shadow: var(--shadow-md);
    background: var(--fsrs-good-hover);
    border-color: var(--fsrs-good-hover);
}

.back-arrow {
    width: 0;
    height: 0;
    border-top: 6px solid transparent;
    border-bottom: 6px solid transparent;
    border-right: 10px solid #ffffff;
}

/* --- Login Page --- */
.login-container {
    width: 100%;
    max-width: 400px;
    padding: 40px;
    background: var(--card-background);
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow-lg);
    text-align: center;
}

.login-container h2 {
    margin-bottom: 30px;
    color: var(--text-main);
}

.login-container label {
    display: block;
    text-align: left;
    margin-bottom: 8px;
    font-weight: 500;
    color: var(--text-secondary);
}

.login-container .form-control {
    margin-bottom: 20px;
}

/* --- Popup --- */
.overlay-popup {
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.35);
    display: none;
    align-items: center;
    justify-content: center;
    z-index: 9999;
}

.popup-card {
    background: #111827;
    color: #ffffff;
    padding: 16px 24px;
    border-radius: 12px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.35);
    font-family: 'Roboto', system-ui, -apple-system, Segoe UI, Helvetica, Arial, sans-serif;
    letter-spacing: 0.2px;
}

.popup-title {
    font-size: 18px;
    font-weight: 600;
}